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Articles

Exchange of Fluid Between Capillaries and Tissues

The distribution of extracellular fluid between the plasma and interstitial compartments is in a state of dynamic equilibrium. Tissue fluid is not normally a stagnant pond rather, it is a continuously circulating medium, formed from and returning to the vascular system. In this way, the tissue cells receive a continuously fresh supply of glucose and other plasma solutes that are filtered through tiny endothelial channels in the capillary walls. Filtration results from blood pressure within the...

Regulation of Blood Volume by the Kidneys

The formation of urine begins in the same manner as the formation of tissue fluid by filtration of plasma through capillary pores. These capillaries are known as glomeruli, and the filtrate they produce enters a system of tubules that transports and modifies the filtrate by mechanisms discussed in chapter 17 . The kidneys produce about 180 L per day of blood filtrate, but since there is only 5.5 L of blood in the body, it is clear that most of this filtrate must be returned to the vascular...

Feedback Control of the Anterior Pituitary

In view of its secretion of releasing and inhibiting hormones, the hypothalamus might be considered the master gland. The chain of command, however, is not linear the hypothalamus and anterior pituitary are controlled by the effects of their own actions. In the endocrine system, to use an analogy, the general takes orders from the private. The hypothalamus and anterior pituitary are not master glands because their secretions are controlled by the target glands they regulate. Anterior pituitary...

The Internal Environment and Homeostasis

An amoeba and a human liver cell both obtain their energy by breaking down certain organic nutrients. The chemical reactions involved in this intracellular process are remarkably similar in the two types of cells and involve the utilization of oxygen and the production of carbon dioxide. The amoeba picks up oxygen directly from the fluid surrounding it its external environment and eliminates carbon dioxide into the same fluid. But how can the liver cell and all other internal parts of the body...

Pressure Changes During the Cardiac Cycle

When the heart is in diastole, pressure in the systemic arteries averages about 80 mmHg millimeters of mercury . These events in the cardiac cycle then occur 1. As the ventricles begin their contraction, the intraventricular pressure rises, causing the AV valves to snap shut. At this time, the ventricles are neither being filled with blood because the AV valves are closed nor ejecting blood because the intraventricular pressure has not risen sufficiently to open the semilunar valves . This is...

Visual Acuity and Sensitivity

While reading or similarly viewing objects in daylight, each eye is oriented so that the image falls within a tiny area of the retina called the fovea centralis. The fovea is a pinhead-sized pit fovea pit within a yellow area of the retina called the macula lutea. The pit is formed as a result of the displacement of neural layers around the periphery therefore, light falls directly on photoreceptors in the center fig. 10.41 . Light falling on other areas, by contrast, must pass through several...

Digestion and Absorption in the Stomach

Proteins are only partially digested in the stomach by the action of pepsin, while carbohydrates and fats are not digested at all by pepsin. Digestion of starch begins in the mouth with the action of salivary amylase and continues for a time when the food enters the stomach, but amylase soon becomes inactivated by the strong acidity of gastric juice. The complete digestion of food molecules occurs later, when chyme enters the small intestine. Therefore, people who have had partial gastric...

Ventilation and Acid Base Balance

The basic concepts and terminology relating to the acid-base balance of the blood were introduced in chapter 13. In brief review, acidosis refers to an arterial pH below 7.35, and alkalosis refers to an arterial pH above 7.45. There are two components of each respiratory and metabolic. The respiratory component refers to the carbon dioxide concentration of the blood, as measured by the PCO2. As implied by its name, the respiratory component is regulated by the respiratory system. The metabolic...

Chemoreceptors in the Medulla

The chemoreceptors most sensitive to changes in the arterial PCO2 are located in the ventral area of the medulla oblongata, near the exit of the ninth and tenth cranial nerves. These chemoreceptor neurons are anatomically separate from, but synaptically communicate with, the neurons of the respiratory control center in the medulla. An increase in arterial PCO2 causes a rise in the H concentration of the blood as a result of increased carbonic acid concentrations. The H in the blood, however,...

Mechanism of Thyroid Hormone Action

As previously discussed, the major hormone secreted by the thyroid gland is thyroxine, or tetraiodothyronine T4 . Like steroid hormones, thyroxine travels in the blood attached to carrier proteins primarily to thyroxine-binding globulin, or TBG . The thyroid also secretes a small amount of triiodothyronine, or T3. The carrier proteins have a higher affinity for T4 than for T3, however, and, as a result, the amount of unbound or free T3 in the plasma is about ten times greater than the amount of...

Hormone Metabolism and Excretion

A hormone's concentration in the plasma depends not only upon its rate of secretion by the endocrine gland but also upon its rate of removal from the blood, either by excretion or by metabolic transformation. The liver and the kidneys are the major organs that excrete or metabolize hormones. The liver and kidneys, however, are not the only routes for eliminating hormones. Sometimes the hormone is metabolized by the cells upon which it acts. Very importantly, in the case of peptide hormones,...

Tonic and Phasic Receptors Sensory Adaptation

Some receptors respond with a burst of activity when a stimulus is first applied, but then quickly decrease their firing rate adapt to the stimulus if the stimulus is maintained. Receptors with this response pattern are called phasic receptors. Receptors that produce a relatively constant rate of firing as long as the stimulus is maintained are known as tonic receptors fig. 10.1 . Phasic receptors alert us to changes in sensory stimuli and are in part responsible for the fact that we can cease...

The Formed Elements of Blood

The formed elements of blood include two types of blood cells erythrocytes, or red blood cells, and leukocytes, or white blood cells. Erythrocytes are by far the more numerous of the two. A cubic millimeter of blood contains 5.1 million to 5.8 million erythrocytes in males and 4.3 million to 5.2 million erythrocytes in females. The same volume of blood, by contrast, contains only 5,000 to 9,000 leukocytes. Erythrocytes are flattened, biconcave discs, about 7 im in diameter and 2.2 im thick....

Maintenance of Upright Posture and Balance

The skeleton supporting the body is a system of long bones and a many-jointed spine that cannot stand erect against the forces of gravity without the support given by coordinated muscle activity. The muscles that maintain upright posture that is, support the body's weight against gravity are controlled by the brain and by reflex mechanisms that are wired into the neural networks of the brainstem and spinal cord. Many of the reflex pathways previously introduced for example, the stretch and...

Grade 3 Tibial Stress Fracture

The tibia is the most common site of stress-related injury in runners 6,8 . Leg pain is common in runners, and may be caused by a number of etiologies, Fig. 5. Navicular stress fracture. A Twenty-seven-year-old female tennis pro with pain and tenderness along the medial aspect of the navicular. Axial T2 SE image shows increased signal intensity within the navicular consistent with bone marrow edema, with a low-signal vertical line interrupting the dorsal cortex, consistent with a stress...

Cellular Distribution of MHC Molecules

In general, the classical class I MHC molecules are expressed on most nucleated cells, but the level of expression differs among different cell types. The highest levels of class I molecules are expressed by lymphocytes, where they constitute approximately 1 of the total plasma-membrane proteins, or some 5 X 105 molecules per cell. In contrast, fibroblasts, muscle cells, liver hepatocytes, and neural cells express very low levels of class I MHC molecules. The low level on liver cells may...

Localized Inflammatory Response

The hallmarks of a localized acute inflammatory response, first described almost 2000 years ago, are swelling tumor , redness rubor , heat calor , pain dolor , and loss of function. Within minutes after tissue injury, there is an increase in vascular diameter vasodilation , resulting in an increase in the volume of blood in the area and a reduction in the flow of blood. The increased blood volume heats the tissue and causes it to redden. Vascular permeability also increases, leading to leakage...

Laparoscopic Revision of Fundoplication

Operative access for technical failures of fundo-plications was originally described using an open abdominal technique or a thoracic approach. In the past 10 years, there have been multiple retrospective reviews of personal expe- REOPERATION FOR FAILED ANTI-REFLUX SURGERY Figure 11.5. Port placement for laparoscopic reoperative fundoplication surgery. LR, liver retractor S, telescope SLH, surgeon's left hand SRH, surgeon's right hand ARH, assistant's right hand. Reproduced with permission from...

Single Unit and Multiunit Smooth Muscles

Smooth muscles are often grouped into two functional categories single-unit and multiunit fig. 12.35 . Single-unit smooth muscles have numerous gap junctions electrical synapses between adjacent cells that weld them together electrically they thus behave as a single unit, much like cardiac muscle. Most smooth muscles including those in the digestive tract and uterus are single-unit. Only some cells of single-unit smooth muscles receive autonomic innervation, but the ACh released by the axon can...

Effects of Blood PO2 on Ventilation

Under normal conditions, blood Po2 affects breathing only indirectly, by influencing the chemoreceptor sensitivity to changes in PcO2- Chemoreceptor sensitivity to PCO gt 2 is augmented by a low PO2 so ventilation is increased at a high altitude, for example and is decreased by a high PO2. If the blood PO2 is raised by breathing 100 oxygen, therefore, the breath can be held longer because the response to increased PCO2 is blunted. When the blood PCO2 is held constant by experimental techniques,...

Refractory Period of the Heart

Ventricular muscle, unlike skeletal muscle, is incapable of any significant degree of summation of contractions, and this is a very good thing. Imagine that cardiac muscle were able to undergo a prolonged tetanic contraction. During this period, no ventricular filling could occur since filling can occur only when the ventricular muscle is relaxed, and the heart would therefore cease to function as a pump. The inability of the heart to generate tetanic contractions is the result of the long...

Pulse Pressure and Mean Arterial Pressure

When someone takes a pulse, he or she palpates an artery for example, the radial artery and feels the expansion of the artery occur in response to the beating of the heart the pulse rate is thus a measure of the cardiac rate. The expansion of the artery with each pulse occurs as a result of the rise in blood pressure within the artery as the artery receives the volume of blood ejected by a stroke of the left ventricle. Since the pulse is produced by the rise in pressure from dia-stolic to...

Organs with Dual Innervation

Most visceral organs receive dual innervation they are innervated by both sympathetic and parasympathetic fibers. In this condition, the effects of the two divisions of the autonomic system may be antagonistic, complementary, or cooperative table 9.7 . The effects of sympathetic and parasympathetic innervation of the pacemaker region of the heart is the best example of the antagonism of these two systems. In this case, sympathetic and parasympathetic fibers innervate the same cells. Adrenergic...

The Loading and Unloading Reactions

Deoxyhemoglobin and oxygen combine to form oxyhemoglo-bin this is called the loading reaction. Oxyhemoglobin, in turn, dissociates to yield deoxyhemoglobin and free oxygen molecules this is the unloading reaction. The loading reaction occurs in the lungs and the unloading reaction occurs in the systemic capillaries. Loading and unloading can thus be shown as a reversible reaction Deoxyhemoglobin O2 lt z gt Oxyhemoglobin tissues The extent to which the reaction will go in each direction depends...

Extracellular Osmolarity and Cell Volume

We can now apply the principles learned about osmosis to cells, which meet all the criteria necessary to produce an osmotic flow of water across a membrane. Both the intracellular and extracellular fluids contain water, and cells are surrounded by a membrane that is very permeable to water but impermeable to many substances nonpenetrating solutes . About 85 percent of the extracellular solute particles are sodium and chloride ions, which can diffuse into the cell through protein channels in the...

The Holding Environment

The frame that supports the analytic relationship is also referred to as the holding environment, an expression that highlights its containing function. Bion 1967 drew a parallel between the mother's capacity to receive the raw intensity of her baby's projections, to empathise and to bear them, thereby rendering them eventually manageable for the baby, and the therapist's function of receiving, containing and transforming the patient's communications. This helps the patient eventually to...

Immune Responses to Extracellular and Intracellular Bacteria Can Differ

Infection by extracellular bacteria induces production of humoral antibodies, which are ordinarily secreted by plasma cells in regional lymph nodes and the submucosa of the respiratory and gastrointestinal tracts. The humoral immune response is the main protective response against extracellular bacteria. The antibodies act in several ways to protect the host from the invading organisms, including removal of the bacteria and inactivation of bacterial toxins Figure 17-8 . Extracellular bacteria...

Body Temperatures And Heat Transfer In The Body

The body is divided into a warm internal core and a cooler outer shell Fig. 29.2 . Because the temperature of the shell is strongly influenced by the environment, its temperature is not regulated within narrow limits as the internal body temperature is, even though thermoregulatory responses strongly affect the temperature of the shell, especially its outermost layer, the skin. The thickness of the shell depends on the environment and the body's need to conserve heat. In a warm environment, the...

Pepsin and Hydrochloric Acid Secretion

The parietal cells secrete H , at a pH as low as 0.8, into the gastric lumen by primary active transport involving carriers that function as an ATPase . These carriers, known as H K ATPase pumps, transport H uphill against a million-to-one concentration gradient into the lumen of the stomach while they transport K in the opposite direction fig. 18.8 . At the same time, the parietal cell's basolateral membrane facing the blood in capillaries of the lamina propria take in Cl-against its...

Involvement of Renal Sympathetic Nerve in Pathogenesis of Hypertension

Hiroo Kumagai, Toshiko Onami, Kamon Iigaya, Chie Takimoto, Masaki Imai, Tomokazu Matsuura, Katsufumi Sakata, Naoki Oshima, Koichi Hayashi, Takao Saruta Department of Internal Medicine, Keio University School of Medicine, Shinjuku-ku, Tokyo, Japan Network of the Sympathetic Nervous System and Baroreflex Figure 1 demonstrates the network of the sympathetic nervous system SNS 1-8 . The rostral ventrolateral medulla RVLM, shaded area contains neurons that stimulate the SNS and determine blood...

Skeletal Muscle Action Potential

Brane potential to change after a stimulus is applied is called the time constant or t, and its relationship to capacitance C and resistance R is defined by the following equation In the absence of an action potential, a stimulus applied to the neuronal membrane results in a local potential change that decreases with distance away from the point of stimulation. The voltage change at any point is a function of current and resistance as defined by Ohm's law. If a lig-and-gated channel opens...

Chemical Classification of Hormones

Hormones secreted by different endocrine glands vary widely in chemical structure. All hormones, however, can be divided into a few chemical classes. 1. Amines. These are hormones derived from the amino acids tyrosine and tryptophan. They include the hormones secreted by the adrenal medulla, thyroid, and pineal glands. 2. Polypeptides and proteins. Polypeptide hormones generally contain less than 100 amino acids an example is antidiuretic hormone table 11.2 . Protein hormones are polypeptides...

Structure of a Long Bone

A typical long bone Fig. 19-5 has a shaft or diaphysis composed of compact bone tissue. Within the shaft is a medullary cavity containing the yellow form of bone marrow, which is high in fat. The irregular epiph-ysis at either end is made of a less dense, spongy bone tissue containing the blood-forming red bone marrow. A thin layer of cartilage covers the epiphysis and protects the bone surface. Between the diaphysis and the epiphysis at each end of the bone, in a region called the metaphysis,...

Hormones That Use Second Messengers

Hormones that are catecholamines epinephrine and norepineph-rine , polypeptides, and glycoproteins cannot pass through the lipid barrier of the target cell's plasma membrane. Although some of these hormones may enter the cell by pinocytosis, most of their effects result from their binding to receptor proteins on the outer surface of the target cell membrane. Since they exert their effects without entering the target cells, the actions of these hormones must be mediated by other molecules within...

Antagonistic Effectors

Most factors in the internal environment are controlled by several effectors, which often have antagonistic actions. Control by antagonistic effectors is sometimes described as push-pull, where the increasing activity of one effector is accompanied by decreasing activity of an antagonistic effector. This affords a finer degree of control than could be achieved by simply switching one effector on and off. Room temperature can be maintained for example, by simply turning an air conditioner on and...

Inspiration and Expiration

Between the bony portions of the rib cage are two layers of intercostal muscles the external intercostal muscles and the internal intercostal muscles fig. 16.14 . Between the costal cartilages, however, there is only one muscle layer, and its fibers are oriented in a manner similar to those of the internal inter-costals. These muscles are therefore called the interchondral part of the internal intercostals. Another name for them is the parasternal intercostals. An unforced, or quiet,...

Enterohepatic Circulation

In addition to the normal constituents of bile, a wide variety of exogenous compounds drugs are secreted by the liver into the bile ducts table 18.2 . The liver can thus clear the blood of particular compounds by removing them from the blood and excreting them into the intestine with the bile. Molecules that are cleared from the blood by secretion into the bile are eliminated in the feces this is analogous to renal clearance of blood through excretion in the urine chapter 17 . Many compounds...

Prohormones and Prehormones

Hormone molecules that affect the metabolism of target cells are often derived from less active parent, or precursor, molecules. In the case of polypeptide hormones, the precursor may be a longer chained prohormone that is cut and spliced together to make the hormone. Insulin, for example, is produced from proinsulin within the beta cells of the islets of Langerhans of the pancreas see fig. 3.25 . In some cases, the prohormone itself is derived from an even larger precursor molecule in the case...

Parasympathetic Division

The parasympathetic division is also known as the craniosacral division of the autonomic system. This is because its preganglionic fibers originate in the brain specifically, in the midbrain, medulla oblongata, and pons and in the second through fourth sacral levels of the spinal column. These pre-ganglionic parasympathetic fibers synapse in ganglia that are located next to or actually within the organs innervated. These parasympathetic ganglia, called terminal ganglia, supply the...

Transport of Lipids in the Blood

Once the chylomicrons are in the blood, their triglyceride content is removed by the enzyme lipoprotein lipase, which is attached to the endothelium of blood vessels. This enzyme hydrolyzes triglycerides and thus provides free fatty acids and Step 1 Emulsification of fat droplets by bile salts Step 2 Hydrolysis of triglycerides in emulsified fat droplets into fatty acid and monoglycerides Step 3 Dissolving of fatty acids and monoglycerides into micelles to produce mixed micelles Figure 18.35...

Intrapulmonary and Intrapleural Pressures

The visceral and parietal pleurae are normally flush against each other, so that the lungs are stuck to the chest wall in the same manner as two wet pieces of glass sticking to each other. The intrapleural space contains only a film of fluid secreted by the two membranes. The pleural cavity in a healthy person is thus potential rather than real it can become real only in abnormal situations when air enters the intrapleural space. Since the lungs normally remain in contact with the chest wall,...

Retrovirus HIV1 Is the Causative Agent of AIDS

Within a few years after recognition of AIDS as an infectious disease, the causative agent was discovered and characterized by efforts in the laboratories of Luc Montagnier in Paris and Robert Gallo in Bethesda Figure 19-8 . This immunodeficiency syndrome was novel at the time in that the type of virus causing it was a retrovirus. Retroviruses carry their genetic information in the form of RNA. When the virus enters a cell, the RNA is reverse transcribed to DNA by a virally encoded enzyme,...

Herpes Simplex Virus Type Ii Hsv2

Genital herpes simplex virus HSV infection is not a reportable disease but is considered to be extremely common in the U.S. with approximately 45 million adults approx 22 of the population aged 15-74 yr estimated to be infected in 1990, based on the serologic results of a random sampling of civilian adults examined as part of the National Health and Nutrition Examination Survey NHANES III 12 . This represents a 32 increase compared to 1978, when the seroprevalence of HSV-2 was 16 among the...

Explain How Valves In Veins Breathing And Skeletal Muscle Contractions Help Venous Blood Return To The Heart

Most of the total blood volume is contained in the venous system. Unlike arteries, which provide resistance to the flow of blood from the heart, veins are able to expand as they accumulate additional amounts of blood. The average pressure in the veins is only 2 mmHg, compared to a much higher average arterial pressure of about 100 mmHg. These values, expressed in millimeters of mercury, represent the hydrostatic pressure that the blood exerts on the walls of the vessels. The low venous pressure...

Structural Organization of the Brain

The brain is composed of an enormous number of association neurons and accompanying neuroglia, arranged in regions and subdivisions.These neurons receive sensory information, direct the activity of motor neurons, and perform such higher brain functions as learning and memory. The central nervous system CNS , consisting of the brain and spinal cord fig. 8.1 , receives input from sensory neurons and directs the activity of motor neurons that innervate muscles and glands. The association neurons...

Twitch Summation and Tetanus

When the muscle is stimulated with a single electric shock of sufficient voltage, it quickly contracts and relaxes. This response is called a twitch. Increasing the stimulus voltage increases the strength of the twitch, up to a maximum. The strength of a muscle contraction can thus be graded, or varied an obvious requirement for the proper control of skeletal movements. If a second electric shock is delivered immediately after the first, it will produce a second twitch that may partially ride...

Endothelial Cells Can Release Chemicals That Cause Relaxation or Constriction of Arterioles

An important contributor to local vascular regulation is released by endothelial cells. This substance, endothelium-derived relaxing factor EDRF , is released from all arteries, microvessels, veins, and lymphatic endothelial cells. EDRF is nitric oxide NO , which is formed by the action of nitric oxide synthase on the amino acid arginine. NO causes the relaxation of vascular smooth muscle by inducing an increase in cyclic guanosine monophosphate cGMP . When cGMP is increased, the smooth muscle...

Bowel Obstruction In The Elderly

Causes of bowel obstruction usually specific to the elderly include sigmoid volvulus, Ogilvie's Syndrome, colon carcinoma, and gallstone ileus. These conditions in the elderly patient can lead to gangrene with resulting perforation. Sigmoid volvulus is 20 times more likely in the patient age 60 yr and greater 19 . This age association may be due to acquired redundancy of the sigmoid colon. High-residue diets are believed to be the causative factor in developing a redundant sigmoid 20 . Other...

Abnormalities in the shape of the chest

Those of clinical importance are as follows. Increase in anteroposterior diameter. In some patients with emphysema, the posterior AP diameter is increased and the two measurements may approximate barrel chest . The degree of chest deformity in emphysema is not a reliable guide to the severity of the functional defect. An increase in anteroposterior diameter may also be due to thoracic kyphosis unrelated to respiratory disease Fig. 4.12 . Thoracic kyphoscoliosis. This ranges in degree from the...

Erection Emission and Ejaculation

Erection, accompanied by increases in the length and width of the penis, is achieved as a result of blood flow into the erectile tissues of the penis. These erectile tissues include two paired structures the corpora cavernosa located on the dorsal side of the penis, and one unpaired corpus spongiosum on the ventral Seminal vesicle Ejaculatory duct Prostate Figure 20.21 The organs of the male reproductive system. The male organs are seen here in a sagittal view. side fig. 20.22 . The urethra...

Pancreatic Islets Islets of Langerhans

On a microscopic level, the most conspicuous cells in the islets are the alpha and beta cells fig. 11.30 . The alpha cells secrete the hormone glucagon, and the beta cells secrete insulin. Alpha cells secrete glucagon in response to a fall in blood glucose concentrations. Glucagon stimulates the liver to Figure 11.29 The actions of parathyroid hormone and the control of its secretion. An increased level of parathyroid hormone causes the bones to release calcium and the kidneys to conserve...

Lung Volumes Affect Pulmonary Vascular Resistance

Pulmonary vascular resistance is also significantly affected by lung volume. Because pulmonary capillaries have little , Measuring pulmonary wedge pressure. A catheter is threaded through a peripheral vein in the systemic circulation, through the right heart, and into the pulmonary artery. The wedged catheter temporarily occludes blood flow in a part of the vascular bed. The wedge pressure is a measure of downstream pressure, which is pulmonary venous pressure. Pulmonary venous pressure...

Length Tension Relationship

The strength of a muscle's contraction is influenced by a variety of factors. These include the number of fibers within the muscle that are stimulated to contract, the frequency of stimulation, the thickness of each muscle fiber thicker fibers have more myofibrils and thus can exert more power , and the initial length of the muscle fibers when they are at rest. There is an ideal resting length for striated muscle fibers. This is the length at which they can generate maximum force. When the...

Clinical and Endoscopic Findings

Patients with acute rhinosinusitis commonly complain of nasal obstruction, rhinorrhea, headache, facial pain, and dysosmia. The occurrence of an orbital complication may be suspected when fever, exacerbation of headache, and ocular symptoms appear Younis et al. 2002a . In the presence of preseptal cellulitis, erythema and edema of the eyelid without ophthalmoplegia or visual loss are observed. When proptosis, chemosis, and impairment of extraocular movement occur, a subperiosteal or...

Herbivores have special adaptations for digesting cellulose

Cellulose is the principal organic compound in the diets of herbivores. Most herbivores, however, cannot produce cellu-lases, the enzymes that hydrolyze cellulose. Exceptions include silverfish insects well known for eating books and stored papers , earthworms, and shipworms. Other herbivores, from termites to cattle, rely on microorganisms living in their digestive tracts to digest cellulose for them. The digestive tracts of ruminants cud chewers such as cattle, goats, and sheep are...

Adrenergic and Cholinergic Synaptic Transmission

Acetylcholine ACh is the neurotransmitter of all preganglionic fibers both sympathetic and parasympathetic . Acetylcholine is also the transmitter released by most parasympathetic post- ganglionic fibers at their synapses with effector cells fig. 9.7 . Transmission at these synapses is thus said to be cholinergic. The neurotransmitter released by most postganglionic sympathetic nerve fibers is norepinephrine noradrenaline . Transmission at these synapses is thus said to be adrenergic. There are...

Intrinsic Regulation of Blood Flow

Intrinsic, or built-in, mechanisms within individual organs provide a localized regulation of vascular resistance and blood flow. Intrinsic mechanisms are classified as myogenic or metabolic. Some organs, the brain and kidneys in particular, utilize these intrinsic mechanisms to maintain relatively constant flow rates despite wide fluctuations in blood pressure. This ability is termed autoregulation. If the arterial blood pressure and flow through an organ are inadequate if the organ is...

Effects of Blood PCO2 and pH on Ventilation

Chemoreceptor input to the brain stem modifies the rate and depth of breathing so that, under normal conditions, arterial PCo2, pH, and Po2 remain relatively constant. If hypoventilation inadequate ventilation occurs, PCO2 quickly rises and pH falls. The fall in pH is due to the fact that carbon dioxide can combine Sensory nerve fibers in vagus nerve Sensory nerve fibers in vagus nerve Figure 16.26 Sensory input from the aortic and carotid bodies. The peripheral chemoreceptors aortic and...

Negative Feedback Control of Calcium and Phosphate Balance

The secretion of parathyroid hormone is controlled by the plasma calcium concentrations. Its secretion is stimulated by low calcium concentrations and inhibited by high calcium concentrations. Since parathyroid hormone stimulates the final hy-droxylation step in the formation of 1,25-dihydroxyvitamin D3, a rise in parathyroid hormone results in an increase in production of 1,25-dihydroxyvitamin D3. Low blood calcium can thus be corrected by the effects of increased parathyroid hormone and...

And Mitochondrial Leukoencephalopathies

Leigh syndrome, also called subacute necrotizing encephalomyelopathy, is a neurodegenerative disorder mainly occurring in infancy and childhood. The disease often starts before 1 year of age and leads to death in months or years. Juvenile and adult-onset forms have also been described. In most cases the disease has an autosomal recessive inheritance in some cases inheritance is maternal or X-linked. Both sexes are affected, but among infants there is a 3 2 male predominance. The course can be...

Labeling Exercise 151

Write the name of each numbered part on the corresponding line of the answer sheet. Anus Cervix Clitoris Cul-de-sac Labium majus Labium minus Ovary Oviduct Posterior fornix Rectum Urethra Female Reproductive System Showing Fertilization Write the name of each numbered part on the corresponding line of the answer sheet. Body of uterus Cervical canal Cervix Fundus of uterus Greater vestibular Bartholin gland Implanted embryo Maturing follicle Ovarian follicle ruptured Oviduct fallopian tube Ovary...

Bone Deposition and Resorption

The skeleton, in addition to providing support for the body, serves as a large store of calcium and phosphate in the form of crystals called hydroxyapatite, which has the formula Cajo PO4 6 OH 2. The calcium phosphate in these hydroxyap-atite crystals is derived from the blood by the action of bone-forming cells, or osteoblasts. The osteoblasts secrete an organic matrix composed largely of collagen protein, which becomes hardened by deposits of hydroxyapatite. This process is called bone...

Hormones That Bind to Nuclear Receptor Proteins

Unlike the water-soluble hormones, the lipophilic steroid and thyroid hormones do not travel dissolved in the aqueous portion of the plasma rather, they are transported to their target cells attached to plasma carrier proteins. These hormones must then dissociate from their carrier proteins in the blood in order to pass through the lipid component of the plasma membrane and enter the target cell, within which their receptor proteins are located fig 11.4 . The receptors for the lipophilic...

Types of Endocrine Disorders

Most endocrine disorders fall into one of four categories 1 too little hormone hyposecretion 2 too much hormone hypersecretion 3 reduced response of the target cells hyporesponsiveness and 4 increased response of the target cells hyperresponsive-ness . In the first two categories, the phrases too little hormone and too much hormone here mean too little or too much for any given physiological situation. For example, as we shall see, insulin secretion decreases during fasting, and this decrease...

Stress Reaction Femur

Stress fractures of the femur in runners may occur in the femoral neck, trochan-teric and subtrochanteric region, and femoral shaft. These injuries are often not considered in the initial presentation, and a high index of suspicion must be maintained. Patients commonly present with hip, groin, gluteal, thigh, or knee pain, depending on the location of the injury 18,72,73 . In a study by Clement and colleagues 72 , 71 patients who had 74 stress fractures of the femur were studied. Nearly 95 were...

Significance of Blood PO and PCO2 Measurements

Since blood PO2 measurements are not directly affected by the oxygen in red blood cells, the PO2 does not provide a measurement of the total oxygen content of whole blood. It does, however, provide a good index of lung function. If the inspired air had a normal PO2 but the arterial PO2 was below normal, for example, you could conclude that gas exchange in the lungs was impaired. Measurements of arterial PO2 thus provide valuable information in treating people with pulmonary diseases, in...

Hormone Production Sexual Development and Activity Hormone Production

Testosterone levels are generally normal in men with cryptorchidism, even those who were not treated 73,130 . Although testosterone levels are within the normal range in men who were formerly cryptorchid see Fig. 3 without other problems, a Fig. 4. Testosterone levels ng dL in men who were formerly cryptorchid plotted against age of orchidopexy. These data suggest lower levels in men with orchiopexy at older ages 1 . Fig. 4. Testosterone levels ng dL in men who were formerly cryptorchid plotted...

Hypogonadism Can Result From Defects at Several Levels

Male hypogonadism may result from defects in spermato-genesis, steroidogenesis, or both. It may be a primary defect in the testes or secondary to hypothalamic-pituitary dysfunction, and determining whether the onset of gonadal failure occurred before or after puberty is important in establishing the cause. However, several factors must be considered. First, normal spermatogenesis almost never occurs with defective steroidogenesis, but normal steroidogenesis can be present with defective...

Central Mechanisms Of Penile Erection And Flaccidity

The cortex receives sensory information from the penis and genitalia. Stimulation of thalamic and cortical areas associated with somatomotor pathways elicits sexual feelings and genital sensations but does not lead to penile erection. Conversely, stimulation of cortical-subcortical areas linked to the limbic system elicit penile erections in response to stimulation, as demonstrated in monkeys 5,171-173 . Direct study of the human brain is limited to observations made during neurosurgical...

Functional Neuroanatomy Of Penile Function

Parasympathetic and Nonadrenergic and Noncholinergic Outflow Parasympathetic preganglionic input to the human penis originates in the sacral S2-S4 spinal cord 30 . In most men, S3 is the main source of erectogenic fibers, with a smaller supply provided by either S2 or S4. These preganglionic neurons are situated in the intermediolateral cell column and send dendritic projections to laminae V, VII, IX, and X of the spinal cord. These distributions for axonal processes imply that sacral...

Long Term Complications

Long-term complications following TURP primarily include urinary tract infection, obstruction, incontinence, and erectile dysfunction, although there is debate about whether the latter is truly associated with the procedure. Interestingly, despite the use of prophylactic and perioperative antibiotics, delayed genitourinary infection is still a significant problem after TURP, accounting for nearly half of long-term complications 4 21 . This is probably not a result of persistent bacteriuria from...

Clinical Aspects of the Male Reproductive System

Most infections of the male reproductive tract are sexually transmitted diseases STDs , listed in Display 14-1. The most common STD in the United States is caused by the bacterium Chlamydia trachomatis, which, in males, mainly causes urethritis. This same organism also causes lymphogranuloma venereum, an STD associated with lymphadenopathy, which is rare in the United States. Both forms of these chlamydial infections respond to treatment with antibiotics. Gonorrhea is caused by Neisseria...

An Oblique Surgical Incision Follows What Direction

Case Study 14-1 Herniorrhaphy and Vasectomy E.D., a 48-year-old married dock worker with three children, developed inguinal bulging and pain on exertion when he lifted heavy objects. An occupational health service advised a surgical referral. The surgeon diagnosed E.D. with bilateral direct inguinal hernias and suggested that he not delay surgery, although he was not at high risk for a strangulated hernia. E.D. asked the surgeon if he could also be sterilized at the same time. He was scheduled...

Sexual Dysfunction Secondary to Surgical Treatment

Sexual dysfunction following rectal surgery for IBD has been reported in 1-27 of cases but dysfunction is often partial and transient 119, 128, 132, 133, 142-148 . This is usually due to damage of neurological structures during pelvic dissection, although psychogenic or vasculogenic factors may contribute 149 . Normal sexual function in males is under the control of both the sympathetic and parasympathetic system erection is mainly mediated by parasympa-thetic fibres, while sympathetic fibres...

Pathophysiology Of Hivinfection In The Reproductive Tract And Potential Mechanisms Of Gonadal Dysfunction

Testicular atrophy is a common finding in autopsy series of patients infected with HIV 8-11 . Histological examination of the testes reveals a spectrum of abnormalities, including hypospermatogenesis, spermatogenic arrest, and Sertoli cell-only pheno-types 11 . In addition to the loss of germ cells and atrophy, the seminiferous tubules exhibit basement membrane thickening and peritubular fibrosis 8,9 . Common abnormalities in semen include leukocytospermia, lower ejaculation volume and total...

The Complement System Clears Immune Complexes from Circulation

The importance of the complement system in clearing immune complexes is seen in patients with the autoimmune disease systemic lupus erythematosus SLE . These individuals produce large quantities of immune complexes and suffer tissue damage as a result of complement-mediated lysis and the induction of type II or type III hypersensitivity see Chapter 16 . Although complement plays a significant role in the development of tissue damage in SLE, the paradoxical finding is that deficiencies in C1,...

Coupled Reactions Oxidation Reduction

When an atom or a molecule gains electrons, it is said to become reduced when it loses electrons, it is said to become oxidized. Reduction and oxidation are always coupled reactions an atom or a molecule cannot become oxidized unless it donates electrons to another, which therefore becomes reduced. The atom or molecule that donates electrons to another is a reducing agent, and the one that accepts electrons from another is an oxidizing agent. It is important to understand that a particular atom...

Physiology Of Cortisol Metabolism

The principal metabolites of cortisol are shown in Figure 18.2. The enzymes directly metabolizing cor tisol include the A-ring reductases 5a- and 5P-reductases , 6 -hydroxylase, 20-reductase, and 11 -hydroxysteroid dehydrogenases. In rats and mice, which lack 17-hydroxylase in their adrenal cortex, the principal glucocorticoid is corticosterone, which is subject to analogous metabolism. 11 P-Hydroxysteroid Dehydrogenases 1ip-HSDs These enzymes catalyse the interconversion of cortisol or...

Androgen And Prostate Growth

The prostate gland is dependent on androgens that are produced exogenously by the testicles to facilitate normal development and to maintain normal structure and function 1 . Briefly, the testes are stimulated to produce and secrete testosterone and other steroids by an exogenous protein, luteinizing hormone, which is made in the pituitary gland. Testosterone T is converted to its reduced form, dihydrotestosterone DHT , by the enzyme 5a-reductase in the prostate. Both T and DHT bind to and...

Immediate Hypersensitivity

Immediate hypersensitivity can produce allergic rhinitis chronic runny or stuffy nose conjunctivitis red eyes allergic asthma atopic dermatitis urticaria, or hives and other symptoms. These symptoms result from the immune response to the allergen. In people who are not allergic, the allergen stimulates one type of helper T lymphocyte, the TH1 cells, to secrete interferon-y and inter-leukin-2. In people who are allergic, dendritic cells stimulate the other type of helper T lymphocytes, the TH2...

Localized Anaphylaxis Atopy

In localized anaphylaxis, the reaction is limited to a specific target tissue or organ, often involving epithelial surfaces at the site of allergen entry. The tendency to manifest localized anaphylactic reactions is inherited and is called atopy. Atopic allergies, which afflict at least 20 of the population in developed countries, include a wide range of IgE-mediated disorders, including allergic rhinitis hay fever , asthma, atopic dermatitis eczema , and food allergies. ALLERGIC RHINITIS The...

Renal Clearance of Inulin Measurement of GFR

If a substance is neither reabsorbed nor secreted by the tubules, the amount excreted in the urine per minute will be equal to the amount that is filtered out of the glomeruli per minute. There does not seem to be a single substance produced by the body, however, that is not reabsorbed or secreted to some degree. Plants such as artichokes, dahlias, onions, and garlic, fortunately, do produce such a compound. This compound, a polymer of the monosaccharide fructose, is inulin. Once injected into...

Tests for nerve root compression

Prolapse of intervertebral discs occurs most frequently at the L4 5 or L5 SI level, producing compression of the L5 and SI nerve roots respectively. Tension can be applied to these nerve roots by flexing the hip with the knee straight -the so-called straight leg raising test. Normally, about 90 degrees of hip flexion should be possible but this varies considerably 70-120 degrees . When the root is stretched over a prolapsed disc, straight leg raising will be restricted and pain will usually be...

Slow and Fast Twitch Fibers

Skeletal muscle fibers can be divided on the basis of their contraction speed time required to reach maximum tension into slow-twitch, or type I, fibers, and fast-twitch, or type II, fibers. These differences are associated with different myosin ATPase isoenzymes, which can also be designated as slow and fast. The two fiber types can be distinguished by their ATPase isoenzyme when they are appropriately stained fig. 12.23 . The extraocular muscles that position the eyes, for example, have a...

The Postoperative Meniscus

All rights reserved. of preserving as much meniscal tissue as possible. Persisting symptoms following meniscal surgery may be from a recurrent tear at the site of previous surgery, the presence of a new tear at a site remote from the previous intervention, or extrameniscal pathology. Accuracy of MRI in assessment of meniscal tears in nonoperated ''virgin'' menisci is well established 5-7 . The MRI criteria for diagnosing meniscal tears in such cases include regions of...

Examples of Autocrine Regulation

Many autocrine regulatory molecules are also known as cy-tokines, particularly if they regulate different cells of the immune system, and as growth factors if they promote growth and cell division in any organ. This distinction is somewhat blurred, however, because some cytokines may also function as growth factors. Cytokines produced by lymphocytes the type of white blood cell involved in specific immunity see chapter 15 are also known as lymphokines, and the specific molecules involved are...

Lipolysis and Reesterification

Adipocytes are highly differentiated cells specialized in handling large quantities of long-chain FA Fig. 11.1 . During lipid storage in the fed state, FA are released by LPL bound to the endothelial capillary wall into the blood from chylomicrons and lipoproteins assembled and secreted by intestinal and liver cells, respectively step 1 , or from albumin, move through the endothelium via passage through tight junctions or endothelial cells step 2 , bind to the outer leaflet of the plasma...

Organization of the Respiratory System

There are two lungs, the right and left, each divided into several lobes. Pulmonary is the adjective referring to lungs. The lungs consist mainly of tiny air-containing sacs called alveoli singular, alveolus , which number approximately 300 million in the adult. The alveoli are the sites of gas exchange with the blood. The airways are all the tubes through which air flows between the external environment and the alveoli. Inspiration inhalation is the movement of air from the external...

Review Activities

Test Your Knowledge ofTerms and Facts 1. Which of these statements is false 2. a. Most of the total blood volume is contained in veins. b. Capillaries have a greater total surface area than any other type of vessel. c. Exchanges between blood and 3. tissue fluid occur across the walls d. Small arteries and arterioles present great resistance to blood flow. All arteries in the body contain oxygen-rich blood with the exception of The lub, or first heart sound, is b. the pulmonary semilunar valve....

Lung Volumes and Capacities

An example of a spirogram is shown in figure 16.16, and the various lung volumes and capacities are defined in table 16.3. A lung capacity is equal to the sum of two or more lung volumes. During quiet breathing, for example, the amount of air expired in each breath is the tidal volume. The maximum amount of air that can be forcefully exhaled after a maximum inhalation is called the vital capacity, which is equal to the sum of the inspiratory reserve volume, tidal volume, and expiratory reserve...

Methods for the Synthesis of Cannabinergic Ligands

Nikas, Richard I. Duclos, Jr., and Alexandros Makriyannis During the last decade, numerous cannabinergic ligands with high affinity and selectivity profiles for cannabinoid receptors CB1 and CB2 emerged from rigorously pursued structure-activity relationship studies. This chapter focuses on the synthetic aspects of key cannabi-noid receptor probes representing the different classes of cannabinergic ligands that encompasses classical cannabinoids CCs including some...

Organs without Dual Innervation

Although most organs are innervated by both sympathetic and parasympathetic nerves, some including the adrenal medulla, ar-rector pili muscles, sweat glands, and most blood vessels receive only sympathetic innervation. In these cases, regulation is achieved by increases or decreases in the tone firing rate of the sympathetic fibers. Constriction of cutaneous blood vessels, for example, is produced by increased sympathetic activity that stimulates alpha-adrenergic receptors, and vasodilation...

Considerations for Esophageal Lengthening Procedures

It is essential that the gastroesophageal junction lie tension free in the abdomen before creating a fundic wrap. The length of tension-free intraabdominal esophagus should be measured after closing the crural defect. When the crura are closed from the caudal condensation of the crural fibers toward the anterior margin of the hiatus, the hiatal orifice is effectively displaced cephalad. This transposition of the hiatal orifice lengthens the intraabdominal segment of esophagus because the...

Microanatomy Of The Lymphatic System

Although there are remarkable similarities in the lymphatic microanatomy within different organs, there are also some essential differences 2 . This review will deal with the common ultrastructural features first and then examine the differences between organs. The lymphatic system Fig. 1 begins as a network of blind ending capillaries which absorb lymph from the interstitial spaces. These capillaries are called initial lymphatics and are also known in the literature as prelymphatics, lymphatic...

Carrier Mediated Transport

Molecules such as glucose are transported across plasma membranes by special protein carriers. Carrier-mediated transport in which the net movement is down a concentration gradient, and which is therefore passive, is called facilitated diffusion. Carrier-mediated transport that occurs against a concentration gradient, and which therefore requires metabolic energy, is called active transport. In order to sustain metabolism, cells must take up glucose, amino acids, and other organic molecules...

The Liver Is Important in Carbohydrate Metabolism

The liver is extremely important in maintaining an adequate supply of nutrients for cell metabolism and regulating blood glucose concentration Fig. 28.3 . After the ingestion of a meal, the blood glucose increases to a concentration of 120 to 150 mg dL, usually in 1 to 2 hours. Glucose is taken up by hepatocytes by a facilitated carrier-mediated process and is converted to glucose 6-phosphate and then UDP-glucose. UDP-glucose can be used for glycogen synthesis, or glycogenesis. It is generally...

Scapholunate Advanced Collapse

Siegel History and Clinical Presentation A 54-year-old right hand dominant man who works as a museum director presented with a 3-year history of gradually increasing pain, swelling, and loss of mobility in his right wrist. He also noted the recent onset of nocturnal paresthesias in the sensory distribution of the median nerve. There was no history of trauma, although he had played professional basketball for 12 years. A wrist splint, nonsteroidal antiinflammatory...

Regulators That Control Genes Of The Vertebrate Immune Systems

The adaptive immune system, with its B- and T-lymphocytes, antigen-dependent clonal selection mechanisms, and antigen-specific immunologic memory, is found only in vertebrates within the chordate assemblage of deuterostomes 56-60 . Supplementing the innate immune system, this results in a layered system of innate and adaptive responses, interconnected and cemented by many potent regulatory links between the two kinds of response 61 . In evolutionary terms, lymphocytes presumably arose by the...

Anterior Tibial Artery Palpation

The anatomy of he radial, brachial and carotid pulses have been described I p. 83 . Femoral artery. The I'emoral artery is situated just below the inguinal ligament, midway between the anterior superior iliac spine and the pubic symphysis mid-inguinal point . It is immediately lateral to the femoral vein and medial to the femoral nerve. In the obese it can be difficult to feel. Popliteal artery. At the level of the knee crease, the artery lies deep in the popliteal fossa and the pulse is...

Diagnostic evaluation

The evaluation of a patient with lower extremity arterial occlusive disease starts with a detailed history and a complete physical examination 1 . A thorough pulse exam of both upper and lower extremities is of outmost importance. Absence of palpable pulses at any level indicates hemodynamically significant lesion s to the main artery proximal to that level. Thus, absence of palpable femoral pulses is suggestive of severe stenosis or occlusion of the ipsilateral iliac artery 2 . Hemodynamic...