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Articles

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...

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...

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...

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...

Circulatory Changes During Exercise

While the vascular resistance in skeletal muscles decreases during exercise, the resistance to flow through the visceral organs and skin increases. This increased resistance occurs because of vasoconstriction stimulated by adrenergic sympathetic fibers, and it results in decreased rates of blood flow through these organs. During exercise, therefore, the blood flow to skeletal muscles increases because of three simultaneous changes 1 increased total blood flow cardiac output 2 metabolic...

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...

Rupture Of The Patellar Tendon

Rupture of the patellar tendon after total knee replacement is a rare and typically devastating problem Fig. 13.1 . Unfortunately, the results of several methods of acute repair are almost uniformly Numerous theories have been postulated to explain the etiology of late rupture of the patellar tendon following TKA. As mentioned previously, improper surgical technique that malaligns the knee or the position of any single component can play a contributory role. Some authors have found its...

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...

Feedback Control of Hormone Secretion

The nature of the endocrine glands, the interaction of the nervous and endocrine systems, and the actions of hormones will be discussed in detail in later chapters. For now, it is sufficient to describe the regulation of hormone secretion very broadly, since it so superbly illustrates the principles of homeostasis and negative feedback regulation. Hormones are secreted in response to specific chemical stimuli. A rise in the plasma glucose concentration, for example, stimulates insulin secretion...

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...

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...

Endocrine Functions of the Testes

Testosterone is by far the major androgen secreted by the adult testis. This hormone and its derivatives the 5a-reduced androgens are responsible for initiation and maintenance of the body changes associated with puberty in males. Androgens are sometimes called anabolic steroids because they stimulate the growth of muscles and other structures table 20.4 . Increased testosterone secretion during puberty is also required for growth of the accessory sex organs primarily the seminal vesicles and...

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,...

Cleavage and Blastocyst Formation

At about 30 to 36 hours after fertilization, the zygote divides by mitosis a process called cleavage into two smaller cells. The rate of cleavage is thereafter accelerated. A second cleavage, which occurs about 40 hours after fertilization, produces four cells. A third cleavage about 50 to 60 hours after fertilization produces a ball of eight cells called a morula mulberry . This very early embryo enters the uterus 3 days after ovulation has occurred fig. 20.43 . Continued cleavage produces a...

Extrinsic Regulation of Blood Flow

The term extrinsic regulation refers to control by the autonomic nervous system and endocrine system. Angiotensin II, for example, directly stimulates vascular smooth muscle to produce generalized vasoconstriction. Antidiuretic hormone ADH also has a vasoconstrictor effect at high concentrations this is why it is also called vasopressin. This vasopressor effect of ADH is not believed to be significant under physiological conditions in humans. Stimulation of the sympathoadrenal system produces...

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...

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...

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,...

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...

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....

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...

Fluid Movement In Capillaries

Hypoxia-Induced Pulmonary Hypertension Hypoxia has opposite effects on the pulmonary and systemic circulations. Hypoxia relaxes vascular smooth muscle in systemic vessels and elicits vasoconstriction in the pulmonary vasculature. Hypoxic pulmonary vasoconstriction is the major mechanism regulating the matching of regional blood flow to regional ventilation in the lungs. With regional hypoxia, the matching mechanism automatically adjusts regional pulmonary capillary blood flow in response to...

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,...

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,...

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...

Natural History Of Cervical Hpv Infection And Csil

There are more than 100 anogenital HPV types and these are generally divided into oncogenic and nononcogenic types by virtue of the frequency of their association with invasive cervical cancer see Chapter 14 . Of the oncogenic types, HPV-16 is the most important because it is the most common type found in cervical cancer, followed by HPV types 18, 31, and 45. HPV 16 alone counts for about 50 of all cervical cancers worldwide 4 . HPV types 18, 31, and 45 are associated with an additional 20 of...

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...

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...

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...

Palpation during inspiration

The liver, gallbladder, spleen and kidneys should be examined in turn during deep inspiration. The key to success is to keep the examining hand still and wait for the organ to descend. One common error is to begin palpation of the liver too close to the costal margin, thereby missing Place the hand flat on the abdomen with the lingers pointing upwards and position the sensing fingers index and middle lateral to the rectus muscle so that the fingertips lie on a line parallel to lhe expected...

Labor and Parturition

Powerful contractions of the uterus are needed to expel the fetus in the sequence of events called labor. These uterine contractions are known to be stimulated by two agents 1 oxytocin, a polypeptide hormone produced in the hypothalamus and released by the posterior pituitary and also produced by the uterus itself , and 2 prostaglandins, a class of cyclic fatty acids with paracrine functions produced within the uterus. The particular prostaglandins PGs involved are PGF2a and PGE2. Labor can...

Paracrine Regulation of Blood Flow

Paracrine regulators, as described in chapter 11, are molecules produced by one tissue that help to regulate another tissue of the same organ. Blood vessels are particularly subject to paracrine regulation. Specifically, the endothelium of the tunica interna produces a number of paracrine regulators that cause the smooth muscle of the tunica media to either relax or contract. The endothelium produces several molecules that promote smooth muscle relaxation, including nitric oxide, bradykinin,...

Anterolateral Pain Pathway

A stimulus that causes or is on the verge of causing tissue damage usually elicits a sensation of pain. Receptors for such stimuli are known as nociceptors. They respond to intense mechanical deformation, excessive heat, and many chemicals, including neuropeptide transmitters, bradykinin, histamine, cytokines, and prostaglandins, several of which are released by damaged cells. These substances act by combining with specific ligand-sensitive ion channels on the nociceptor plasma membrane. Vander...

Review Activities

Test Your Knowledge ofTerms and Facts menstrual phase a. high estrogen and follicular phase luteal phase ovulation b. low estrogen and progesterone d. increasing estrogen low LH and low progesterone 5. A person with the genotype XO has 6. An embryo with the genotype XX develops female accessory sex organs because of FSH is not secreted by the pituitary. FSH receptors are located in the Leydig cells. FSH receptors are located in the spermatogonia. FSH receptors are located in the Sertoli cells....

Intracellular Events Also Regulate Mast Cell Degranulation

The cytoplasmic domains of the p and 7 chains of FceRI are associated with protein tyrosine kinases PTKs . Crosslink-age of the FceRI receptors activates the associated PTKs, resulting in the phosphorylation of tyrosines within the ITAMs of the 7 subunit as well as phosphorylation of residues on the p subunit and on phospholipase C. These phos-phorylation events induce the production of a number of second messengers that mediate the process of degranulation Figure 16-6 . Within 15 s after...

The Liver Plays an Important Role in the Metabolism of Lipids

The liver plays a pivotal role in lipid metabolism Fig. 28.4 . It takes up free fatty acids and lipoproteins complexes of lipid and protein from the plasma. Lipid is circulated in the plasma as lipoproteins because lipid and water are not mis- The Metabolism of Monosaccharides. Monosaccharides are first phosphorylated by a reaction catalyzed by the enzyme hexokinase. In the liver but not in the muscle , there is a specific enzyme glucokinase for the phosphorylation of glucose to form glucose...

Inspection And Palpation Of The Precordium

Inspection and palpation of the cardiac pulsations of the anterior chest have been practiced by physicians since ancient times and have a solid scientific basis. The results of precordial inspection and palpation have been correlated with noninvasive studies, hemodynamic data, and surgical and autopsy studies202,203 and remain an important part of the cardiovascular examination. Their usefulness depends on an understanding of cardiovascular physiology, the proficiency of the examiner, and his...

Responses to Adrenergic Stimulation

Adrenergic stimulation by epinephrine in the blood and by norepinephrine released from sympathetic nerve endings has both excitatory and inhibitory effects. The heart, dilatory muscles of the iris, and the smooth muscles of many blood vessels are stimulated to contract. The smooth muscles of the bronchioles and of some blood vessels, however, are inhibited from contracting adrenergic chemicals, therefore, cause these structures to dilate. Since excitatory and inhibitory effects can be produced...

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...

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...

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,...

Motor Control Hierarchy

Throughout the central nervous system, the neurons involved in controlling the motor neurons to skeletal muscles can be thought of as being organized in a hierarchical fashion, each level of the hierarchy having a certain task in motor control Figure 12-1 . To begin a movement, a general intention such as pick up sweater or write signature or answer telephone is generated at the highest level of the motor control hierarchy. This highest level encompasses many regions of the brain, including...

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...

Functional Vascular And Microscopic Anatomy Of Penile Erection

Three spongy cylinders comprise the human penis the paired corpora cavernosa runs dorsolaterally and the corpus spongiosum runs ventrally. Incomplete septa between the corpora cavernosa allow for neurovascular communication, allowing the two bodies to function physiologically and pharmacologically as a single unit. The three corporal bodies are enveloped by a dense fascial structure known as the tunica albuginea. The deep fascia Buck's fascia ofthe penis surrounds the outside ofthe tunica...

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...

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...

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...

Female sex organs produce eggs receive sperm and nurture the embryo

When a mammalian egg matures, it is released from the ovary directly into the body cavity. But the egg does not go far. Each ovary is enveloped by the undulating, fringed opening of an oviduct also known as a Fallopian tube , which sweeps the egg into that tube Figure 43.11 . Fertilization takes place in the oviduct. Whether or not the egg is fertilized, cilia lining the oviduct propel it slowly toward the uterus, a muscular, thick-walled cavity shaped in humans like an upside-down pear. The...

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...

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...

Instrumentation in Total Knee Arthroplasty

In the early 1970s the total condylar knee arthroplasty was designed at the Hospital for Special Surgery and emphasized the concepts of ligament balance and knee alignment.1 After the introduction of polymethylmethacrylate, there was a rapid increase in design work because the major obstacle of fixation was relieved. Although the knee implant designs continued to undergo refinement, instrumentation lagged significantly behind the design technology. This dichotomy occurred because the emphasis...

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...

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...

Killer Helper and Suppressor T Lymphocytes

The killer, or cytotoxic, T lymphocytes can be identified in the laboratory by a surface molecule called CD8. Their function is to destroy body cells that harbor foreign molecules. These are usually molecules from an invading microorganism, but they can also be molecules produced by the cell's genome because of a malignant transformation, or they may simply be body molecules that had never been presented before to the immune system. In contrast to the action of B lymphocytes, which kill at a...

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...

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...

Management Of Delayed Puberty

For induction of puberty in boys with constitutional delay of puberty, the indication for treatment is usually psychosocial boys with delayed puberty may suffer because of short stature and lack of pubertal progression. This distress may affect their school performance and their social relationships. Testosterone esters, given intramuscularly, remain the most commonly used treatment approach therapy can be started with 50 mg of a mixture of testosterone propionate and testosterone enanthate...

Methods For Anthropometric Measurements

Weight is measured by digital scales or beam balance to the nearest 100 g. For those unable to stand, electronic chair scales Weighcare C, Marsden Ltd, London are available. For field work, portable scales are used. Equipment is calibrated regularly by standard weights 4 x 10 kg and 8 x 10 kg , and the results of test weighing recorded in a book. Subjects are weighed in light clothing, fasting and with an empty bladder, preferably at the same time of day. Height is measured by stadiometer to...

Endocrine Functions of the Placenta

The placenta secretes both steroid hormones and protein hormones. The protein hormones include chorionic gonadotropin hCG and chorionic somatomammotropin hCS , both of which have actions similar to those of some anterior pituitary hormones table 20.7 . Chorionic gonadotropin has LH-like effects, as previously described it also has thyroid-stimulating ability, like pituitary TSH. Chorionic somatomammotropin likewise has actions that are similar to two pituitary hormones growth hormone and...

Asexual Plant Propagation

In recent years, we have heard amazing stories about scientists who have cloned animals such as sheep and cows. Botanists are far ahead in that arena. They have been cloning plants for centuries Many plants are easy to propagate asexually, using vegetative parts rather than seeds. For example, crown division is a simple technique in which a plant is separated into several pieces, each of which contains a crown and a portion of the root system Fig. 14.17 . This is commonly used for many...

The Indicator Dilution Method Measures Fluid Compartment Size

The indicator dilution method can be used to determine the size of body fluid compartments see Chapter 14 . A known amount of a substance the indicator , which should be confined to the compartment of interest, is administered. After allowing sufficient time for uniform distribution of the indicator throughout the compartment, a plasma sample is collected. The concentration of the indicator in the plasma at equilibrium is measured, and the distribution volume is calculated from this formula...

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...

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...

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...

Immobilization of Microalgae

Several microalgae synthesize metabolites of great commercial interest. Microalgae also act as filters for wastewater N and P, heavy metals, and xenobiotic compounds. However, the cost-effective harvesting of microalgae is one of the major bottlenecks limiting the microalgal biomass applications. In this context, immobilization of algal cells has been proposed for circumventing the harvest problem as well as retaining the high-value algal biomass for further processing. In recent years,...

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...

Digestion and Absorption of Proteins

Protein digestion begins in the stomach with the action of pepsin. Some amino acids are liberated in the stomach, but the major products of pepsin digestion are short-chain polypeptides. Figure 18.32 The action of pancreatic amylase. Pancreatic amylase digests starch into maltose, maltriose, and short oligosaccharides containing branch points in the chain of glucose molecules. Pepsin digestion helps to produce a more homogenous chyme, but it is not essential for the complete digestion of...

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...

Diseases of the Thyroid

Thyroid-stimulating hormone TSH from the anterior pituitary stimulates the thyroid to secrete thyroxine however, it also exerts a trophic growth-stimulating effect on the thyroid. This trophic effect is evident in people who develop an iodine-deficiency endemic goiter, or abnormal growth of Monoiodotyrosine MIT Diiodotyrosine DIT Figure 11.23 The production and storage of thyroid hormones. Iodide is actively transported into the follicular cells. In the colloid, it is converted into iodine and...

Craniospinal Radiation

This technique treats the entire craniospinal axis and frequently is utilized with a high rate of success in other malignant diseases of the craniospinal axis, such as medulloblastoma and central nervous system CNS germinoma. Because of the compartmental nature of leptomeningeal carcinomatosis, craniospinal irradiation is occasionally used in the treatment of this disease process. It involves a technically complex set-up of two opposed lateral brain fields and one or two posterior spine fields...

Muscle Cells Obtain ATP From Several Sources

Although ATP is the immediate fuel for the contraction process, its concentration in the muscle cell is never high enough to sustain a long series of contractions. Most of the immediate energy supply is held in an energy pool of the compound creatine phosphate or phosphocreatine PCr , which is in chemical equilibrium with ATP. After a molecule of ATP has been split and yielded its energy, the resulting ADP molecule is readily rephosphorylated to ATP by the high-energy phosphate group from a...

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...

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...

Anal Skin Tags and Haemorrhoids

Anal skin tags are typically asymptomatic and present problems only when they interfere with perianal hygiene Fig. 5 . They are more prominent with active intestinal disease. Approximately 25 resolve spontaneously, generally after remission of concomitant bowel disease. These tags should not be removed Fig. 5. Anal tags with ulceration and tissue inflammation Fig. 5. Anal tags with ulceration and tissue inflammation because that may result in an unhealed wound, a chronic ulcer or perianal...

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...

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...

Mediastinoscopy Case Study

Case Study 11-1 Preoperative Testing in a Patient With Asthma A.D., 15 years old, was seen in the preadmission testing unit in preparation for her elective spinal surgery. She has a history of mild asthma since age 4, with at least one attack per week. In an acute attack, she will have mild dyspnea, diffuse wheezing, yet an adequate air exchange that responds to bron-chodilators. She was sent to pulmonary health services for a consult with a specialist and pulmonary function studies to clear...

Sequence of Excitation

To reiterate, the SA node is the normal pacemaker for the entire heart. Its depolarization normally generates the current that leads to depolarization of all other cardiac muscle cells, and so its discharge rate determines the heart rate, the number of times the heart contracts per minute. The action potential initiated in the SA node spreads throughout the myocardium, passing from cell to cell by way of gap junctions. The spread Vander et al. Human Physiology The Mechanism of Body Function,...

Regulation of Insulin and Glucagon Secretion

Insulin and glucagon secretion is largely regulated by the plasma concentrations of glucose and, to a lesser degree, of amino acids. The alpha and beta cells, therefore, act as both the sensors and effectors in this control system. Since the plasma concentration of glucose and amino acids rises during the absorption of a meal and falls during fasting, the secretion of insulin and glucagon likewise fluctuates between the absorptive and postabsorptive states. These changes in insulin and...

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...

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...

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...

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...

Development of Accessory Sex Organs and External Genitalia

In addition to testes and ovaries, various internal accessory sex organs are needed for reproductive function. Most of these are derived from two systems of embryonic ducts. Male accessory organs are derived from the wolffian mesonephric ducts, and female accessory organs are derived from the mullerian paramesonephric ducts fig. 20.5 . Interestingly, the two duct systems are present in both male and female embryos between day 25 and day 50, and so embryos of both sexes have the potential to...

Medial Release for Fixed Varus Deformity

Scuderi, and John N. Insall Varus deformity of the knee is one of the most common deformities seen at the time of total knee arthroplasty. When a fixed deformity is present, the pathoanatomy usually involves erosion of medial tibial bone stock with medial tibial osteophyte formation, and contractures of the medial collateral ligament MCL , pos-teromedial capsule, pes anserinus, and semimembranosus muscle Fig. 3.1 . Elongation of the lateral collateral ligament is a...

Passive Immunization Involves Transfer of Preformed Antibodies

Jenner and Pasteur are recognized as the pioneers of vaccination, or induction of active immunity, but similar recognition is due to Emil von Behring and Hidesaburo Kitasato for their contributions to passive immunity. These investigators were the first to show that immunity elicited in one animal can be transferred to another by injecting it with serum from the first see Clinical Focus, Chapter 4 . Passive immunization, in which preformed antibodies are transferred to a recipient, occurs...

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...

Spermatogenesis Stimulation

The induction of spermatogenesis in patients with hypogonadotropic hypogonadism requires testicular stimulation with GnRH or gonadotropins. Various preparations are available see Table 1 to reach this goal, each with advantages and disadvantages. Because the maturation of spermatogonia to mature sperm takes approx 70 d, the first sperm usually do not appear in the ejaculate for at least 3 mo, but it may take 2 yr for patients with congenital hypogonadotropic hypogonadism to become sperm...

Human Papilloma Virus

Human papilloma virus HPV infections have two important clinical manifestations external genital warts EGWs and squamous intraepithelial lesions 30 . A discussion of these neoplasms is beyond the scope of this chapter but screening and treatment issues can be found elsewhere 2 . The majority of newly acquired HPV infections are asymptomatic. EGWs are diagnosed when visible warts occur in the genital area they can be discrete or coalesce into confluent plaques 30 . The acetowhite test has not...

Generator Receptor Potential

The electrical behavior of sensory nerve endings is similar to that of the dendrites of other neurons. In response to an environmental stimulus, the sensory endings produce local graded changes in the membrane potential. In most cases, these potential changes are depolarizations that are analogous to the excitatory postsynaptic potentials EPSPs described in chapter 7. In the sensory endings, however, these potential changes in response to environmental stimulation are called receptor, or...

Velocity of Capillary Blood Flow

Figure 14-44 illustrates a simple mechanical model of a series of 1-cm-diameter balls being pushed down a single tube that branches into narrower tubes. Although each tributary tube has a smaller cross section than the wide tube, the sum of the tributary cross sections is three times greater than that of the wide tube. Let us assume that in the wide tube each ball moves 3 cm min. If the balls are 1 cm in diameter and they move two abreast, six balls leave the wide tube per minute and enter the...

Monoamines as Neurotransmitters

A variety of chemicals in the CNS function as neurotransmitters. Among these are the monoamines,a chemical family that includes dopamine,norepinephrine,and serotonin. Although these molecules have similar mechanisms of action, they are used by different neurons for different functions. The regulatory molecules epinephrine, norepinephrine, dopamine, and serotonin are in the chemical family known as monoamines. Serotonin is derived from the amino acid tryptophan. Epinephrine, norepinephrine, and...

Antigen Selection of Lymphocytes Causes Clonal Expansion

A mature immunocompetent animal contains a large number of antigen-reactive clones of T and B lymphocytes the antigenic specificity of each of these clones is determined by the specificity of the antigen-binding receptor on the mem- Processing and presentation of exogenous and endogenous antigens. a Exogenous antigen is ingested by endocytosis or phagocytosis and then enters the endocytic processing pathway. Here, within an acidic environment, the antigen is degraded into small peptides, which...

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...

Autonomic Nervous System

The efferent innervation of all tissues other than skeletal muscle is by way of the autonomic nervous system. A special case occurs in the gastrointestinal tract, where autonomic neurons innervate a nerve network in the wall of the intestinal tract. This network, termed the enteric nervous system, will be described in Chapter 17. In the autonomic nervous system, parallel chains, each with two neurons, connect the central nervous system and the effector cells Figure 8-43 . This is in contrast to...

Spiral Organ Organ of Corti

The sensory hair cells are located on the basilar membrane, with their hairs actually stereocilia projecting into the endolymph of the cochlear duct. These hair cells are arranged to form one row of inner cells, which extends the length of the basilar membrane, and multiple rows of outer hair cells three rows in the basal turn, four in the middle turn, and five in the apical turn of the cochlea fig. 10.21 . The stereocilia of the outer hair cells are embedded in a gelatinous tectorial membrane...

Exchange of Gases in Alveoli and Tissues

We have now completed our discussion of the lung mechanics that produce alveolar ventilation, but this is only the first step in the respiratory process. Oxygen must move across the alveolar membranes into the pulmonary capillaries, be transported by the blood to the tissues, leave the tissue capillaries and enter the extracellular fluid, and finally cross plasma membranes to gain entry into cells. Carbon dioxide must follow a similar path in reverse. In the steady state, the volume of oxygen...