Female sex organs produce eggs receive sperm and nurture the embryo

Vagina Sperm

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...

Herbivores have special adaptations for digesting cellulose

Large Intestine Ruminant

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...

CO2 is transported as bicarbonate ions in the blood

Co2 Red Blood Cells

Delivering O2 to the tissues is only half of the respiratory function of the blood. The blood also must take carbon dioxide, a metabolic waste product, away from the tissues Figure 48.14 . CO2 is highly soluble and readily diffuses through cell membranes, moving from its site of production in the tissues into the blood, where the partial pressure of carbon dioxide Pco2 is lower. However, very little dissolved CO2 is transported by the blood. Most CO2 produced by the tissues is transported to...

Structure Function and Information Flow

Forebrain Structure And Function

The human nervous system consists of three major components. The brain and spinal cord together constitute the central nervous system CNS . Information is transmitted to and from the CNS by means of an enormous network of nerves that make up the peripheral nervous system PNS . The PNS reaches every tissue of the body. It connects to the CNS via spinal nerves and cranial nerves. A nerve is a bundle of axons that carries information about many things simultaneously. It is important to distinguish...

Cell Recognition and Adhesion

Complementary Proteins

Some organisms, such as bacteria, are unicellular that is, the entire organism is a single cell. Others, such as plants and animals, are multicellular composed of many cells. Often these cells exist in specialized blocks of cells with similar functions, called tissues. Your body has about 60 trillion cells, arranged in different kinds of tissues such as muscle, nerve, skin, and so forth. Two processes allow cells to arrange themselves in groups Cell recognition, in which one cell specifically...

Angiosperms perform double fertilization

Zygote Formation Flowers

In most angiosperm species, the mature pollen grain consists of two cells, the tube cell and the generative cell. The larger tube cell encloses the much smaller generative cell. Guided by the tube cell nucleus, the pollen tube eventually grows through the megasporangial tissue and reaches the embryo sac. The generative cell meanwhile has undergone one mitotic division and cytokinesis to produce two hap-loid sperm cells. Both of the sperm cells enter the embryo sac, where they are released into...

Childbirth is triggered by hormonal and mechanical stimuli

Labor Contraction Feedback Loop

We traced the development of a human blastocyst into an embryo and then a fetus in Chapter 20. Throughout pregnancy, the muscles of the uterine wall periodically undergo slow, weak, rhythmic contractions called Braxton-Hicks contractions. These contractions become gradually stronger during the third trimester of pregnancy and are sometimes called false labor contractions. True labor contractions usually mark the beginning of childbirth. Both hormonal and mechanical stimuli contribute to the...

Nitrogenase catalyzes nitrogen fixation

Plant Root Bacteroid Nitrogenase

Nitrogen fixation is the reduction of nitrogen gas. It proceeds by the stepwise addition of three pairs of hydrogen atoms to N2 Figure 37.6 . In addition to N2, these reactions require The enzyme nitrogenase binds a molecule of nitrogen gas. 2 A reducing agent transfers three successive pairs of hydrogen atoms to N2. 37.6 Nitrogenase Fixes Nitrogen Throughout the chemical reactions of nitrogen fixation, the reactants are bound to the enzyme nitrogenase. A reducing agent transfers hydrogen atoms...

The Endomembrane System

Golgi Complex Packing And Transporting

Much of the volume of some eukaryotic cells is taken up by an extensive endomembrane system. This system includes two main components, the endoplasmic reticulum and the Golgi apparatus. Continuities between the nuclear envelope and the endomembrane system are visible under the electron microscope. Tiny, membrane-surrounded droplets called vesicles appear to shuttle between the various components of the endomembrane system. This system has various structures, but all of them are essentially...

Reptiles have exquisite control of pulmonary and systemic circulation

Reptiles Mixed Oxygenated Blood

Turtles, snakes, and lizards are commonly said to have three-chambered hearts, while crocodilians crocodiles and alligators are said to have four-chambered hearts. But this statement is an oversimplification. The hearts of all these animals have two separate atria and a ventricle that is divided in a complex way so that mixing of oxygenated and deoxy-genated blood is minimized. The reptilian ventricle is partly divided by a septum, which directs oxygenated blood to the body and deoxygenated...

Male sexual function is controlled by hormones

Spermatogenesis

Spermatogenesis and maintenance of male secondary sexual characteristics depend on testosterone, which is produced by the Leydig cells of the testes. As we saw in Chapter 42, increased production of testosterone at puberty is due to an increased release of gonadotropin-releasing hormone GnRH by the hypothalamus, which stimulates cells in the anterior pituitary to increase their secretion of luteinizing hormone LH and follicle-stimulating hormone FSH Figure 43.10 . Higher levels of LH stimulate...

Spraying Dwarf Plants With Gibberelin

Plants Without Gibberellins

Gibberellin Aj important in stem growth Gibberellin A3 commercially available In 1809, the study of the gibberellins began indirectly with observations of the bakanae, or foolish seedling, disease of rice. Seedlings affected by this disease grow tall more rapidly than their healthy neighbors, but this rapid growth gives rise to spindly plants that die before producing seeds the rice grains used for food . The disease has had considerable economic impacts in several parts of the world. It is...

General Biology of the Fungi

The kingdom Fungi encompasses heterotrophic organisms with absorptive nutrition and with chitin in their cell walls. The fungi live by absorptive nutrition They secrete digestive enzymes that break down large food molecules in the environment, and then absorb the breakdown products. Many fungi are saprobes that absorb nutrients from dead matter, others are parasites that absorb nutrients from living hosts Figure 31.1 , and still others are mutualists that live in intimate association with other...

Steps Of Muscle Contraction

Myofibrils Micrograph

RESULTS Autonomic neurotransmitters alter membrane resting potential and thereby determine the rate that smooth muscle cells fire action potentials. Conclusion Smooth muscle contraction is stimulated by stretch and by the parasympathetic neurotransmitter acetylcholine. 47.2 Mechanisms of Smooth Muscle Activation Stretching depolarizes the membrane of smooth muscle cells, and this depolarization causes action potentials that activate the contractile mechanism.The neurotransmitters acetylcholine...

Tissues Organs and Organ Systems

Four Types Tissue

Cells are the basic building blocks of multicellular animals. When cells with the same characteristics or specializations are grouped together, they form a tissue. There are four basic types of tissues epithelial, connective, muscle, and nervous but there are variations on each basic type. An organ is usually made up of several different tissue types Figure 41.2 . 41.2 Four Types of Tissue All cells can be classified into one of four tissue types. An organ such as the stomach is made up of...

The adrenal gland is two glands in one

Amine Hormone Adrenal Medulla

An adrenal gland sits above each kidney, just below the middle of your back. Functionally and anatomically, each adrenal gland consists of a gland within a gland Figure 42.10 . The core, called the adrenal medulla, produces the hormone epinephrine also known as adrenaline and, to a lesser degree, norepinephrine or noradrenaline , which also acts as a neurotransmitter in the nervous system . Surrounding the medulla is the adrenal cortex, which produces other hormones. The medulla develops from...

Fertilization Of Flowers

Sequence Fertilisation Flowers

30.7 A Generalized Flower Not all flowers possess all the structures shown here, but they must possess a stamen bearing microsporangia , a pistil containing megasporangia , or both in order to play their role in reproduction. Flowers that have both, as this one does, are referred to as perfect. mens, and carpels which are referred to as the floral organs see Figure 19.12 are usually positioned in circular arrangements or whorls and attached to a central stalk called the receptacle. The...

Cancer cells differ from their normal counterparts

Cancer cells differ from the normal cells from which they originate in two major ways. CANCER CELLS LOSE CONTROL OVER CELL DIVISION. Most cells in the body divide only if they are exposed to extracellular influences, such as growth factors or hormones. Cancer cells do not respond to these controls, and instead divide more or less continuously, ultimately forming tumors large masses of cells . By the time a physician can feel a tumor or see one on an X ray or CAT scan, it already contains...

Functional Subsystems of the Nervous System

Gyri Function

We have just surveyed the development of the nervous system in terms of anatomically distinct structures. At any one time, these various structures are engaged in many simultaneous tasks a property known as parallel processing of information. Specific tasks are carried out by subsystems that may involve several different anatomical regions or structures of the nervous system. We will now examine several of these functional subsystems. The spinal cord receives and processes information from the...