Human a&p 2
College: Second year
Identify the organs forming the respiratory passageway(s) in descending order until the alveoli are reached.
Distinguish between conducting and respiratory zone structures.
• The bronchial tree is the site where conducting zone structures give way to respiratory zone structures. The conducting zone is made up of passageways for air to travel. These passageways branch into smaller and smaller passages until it gives way to the bronchial tree. The air pathway inferior to the larynx consists of the trachea and the main, lobar, and segmental bronchi, which branch into the smaller bronchi and bronchioles until the terminal bronchioles of the lungs are reached.
• The respiratory zone begins as the terminal bronchioles feed into respiratory bronchioles within the lung. The respiratory bronchioles lead into winding alveolar ducts, whose walls consist of diffusely arranged rings of smooth muscle cells, connective tissue fibers, and outpocketing alveoli. The alveolar ducts lead into terminal clusters of alveoli called alveolar sacs. The 300 million or so gas-filled alveoli in the lungs account for most of the lung volume and provide a tremendous surface area for gas exchange.
Describe the makeup of the respiratory membrane, and relate structure to function.
The walls of the alveoli are composed primarily of a single layer of squamous epithelial cells, called type I cells, surrounded by a flimsy basement membrane. The thinness of their walls is hard to imagine, but a sheet of tissue paper is 15 times thicker. The external surfaces of the alveoli are densely covered with a “cobweb” of pulmonary capillaries. Together, the alveolar and capillary walls and their fused basement membranes form the respiratory membrane, an air-blood barrier that has gas on one side and blood flowing past on the other
Scattered amid the type I squamous cells that form the major part of the alveolar walls are cuboidal type II cells. The type II cells secrete a fluid containing a detergent-like substance called surfactant that coats the gas exposed alveolar surfaces and they also secrete a number of antimicrobial proteins that are important elements of innate immunity.
Describe the gross structure of the lungs and pleurae.
Lungs - Each cone-shaped lung is surrounded by pleurae and connected to the mediastinum by vascular and bronchial attachments, collectively called the lung root. The anterior, lateral, and posterior lung surfaces lie in close contact with the ribs and form the continuously curving costal surface. Just deep to the clavicle is the apex, the narrow superior tip of the lung. The concave, inferior surface that rests on the diaphragm is the base. The two lungs differ slightly in shape and size because the apex of the heart is slightly to the left of the median plane. The left lung is smaller than the right, and the cardiac notch—a concavity in its medial aspect—is molded to and accommodates the heart. The left lung is subdivided into superior and inferior lobes by the oblique fissure, whereas the right lung is partitioned into superior, middle, and inferior lobes by the oblique and horizontal fissures.
Pleurae - form a thin, double-layered serosa. The layer called the parietal pleura covers the thoracic wall and superior face of the diaphragm (Figure 22.10a, c). It continues around the heart and between the lungs, forming the lateral walls of the mediastinal enclosure and snugly enclosing the lung root. From here, the pleura extends as the layer called the visceral pleura to cover the external lung surface, dipping into and lining its fissures.
Explain the functional importance of the partial vacuum that exists in the intrapleural space.
Intrapulmonary pressure is the pressure in the alveoli, which rises and falls during respiration, but always eventually equalizes with atmospheric pressure.
Intrapleural pressure is the pressure in the pleural cavity. It also rises and falls during respiration, but is always about 4 mm Hg less than intrapulmonary pressure.
The amount of pleural fluid in the pleural cavity must remain minimal in order for the negative Pip to be maintained. The pleural fluid is actively pumped out of the pleural cavity into the lymphatics continuously. If it wasn’t, fluid would accumulate in the intrapleural space (remember, fluids move from high to low pressure), producing a positive pressure in the pleural cavity.
Thoracic cavity is a gas-filled box with a single entrance at the top, the tubelike trachea. The volume of this box is changeable and can be increased by enlarging all of its dimensions, thereby decreasing the gas pressure inside it. This drop in pressure causes air to rush into the box from the atmosphere, because gases always flow down their pressure gradients.
Explain the relative roles of the respiratory muscles and lung elasticity in producing the volume changes that cause air to flow into and out of the lungs
• Action of the diaphragm. When the dome-shaped diaphragm contracts, it moves inferiorly and flattens out. As a result, the superior-inferior dimension (height) of the thoracic cavity increases.
• Action of the intercostal muscles. Contraction of the external intercostal muscles lifts the rib cage and pulls the sternum superiorly. Because the ribs curve downward as well as forward around the chest wall, the broadest lateral and anteroposterior dimensions of the rib cage are normally directed obliquely downward. But when the ribs are raised and drawn together, they swing outward, expanding the diameter of the thorax both laterally and in the anteroposterior plane. This is much like the action that occurs when a curved bucket handle is raised—it moves outward as it moves upward.
List several physical factors that influence pulmonary ventilation.
Inspiratory muscles consume energy to overcome three factors that hinder air passage and pulmonary ventilation
• Airway resistance
o increased resistance causes decreased air flow
o Occurs at larger bronchioles – smooth muscle constriction
• Alveolar surface tension
o Due to high amount of water in alveoli sides want to stick together (H bonding)
o Surfactant: contains lipids and proteins that decrease surface tension of water
• Lung compliance: distensibility of lungs
Describe the neural controls of respiration.
Compare the causes and consequences of chronic bronchitis, emphysema, asthma, tuberculosis, and lung cancer.
• Emphysema is characterized by permanently enlarged alveoli and deterioration of alveolar walls.
• Chronic bronchitis results in excessive mucus production, as well as inflammation and fibrosis of the lower respiratory mucosa.
• Asthma is characterized by coughing, dyspnea, wheezing, and chest tightness, brought on by active inflammation of the airways
• Tuberculosis (TB) is an infectious disease caused by the bacterium Mycobacterium tuberculosis and spread by coughing and inhalation
• Lung Cancer
o In both sexes, lung cancer is the most common type of malignancy, and is strongly correlated with smoking.
o Squamous cell carcinoma arises in the epithelium of the bronchi, and tends to form masses that hollow out and bleed.
o Adenocarcinoma originates in peripheral lung areas as nodules that develop from bronchial glands and alveolar cells.
o Small cell carcinoma contains lymphocyte-like cells that form clusters within the mediastinum and rapidly metastasize.
Describe the function of the digestive system, and differentiate between organs of the alimentary canal and accessory digestive organs.
•The digestive system takes in food, breaks it down into nutrient molecules, absorbs these molecules into the bloodstream, and then rids the body of the indigestible remains.
•Digestive system organs fall into two main groups: the alimentary canal and the accessory organs (pp. 852–853).
oThe alimentary canal, or gastrointestinal (GI) tract, is the continuous muscular digestive tube that winds through the body digesting and absorbing foodstuff; its organs include: the mouth, pharynx, esophagus, stomach, small intestine, and large intestine.
oAccessory digestive organs aid digestion physically and produce secretions that break down foodstuff in the GI tract; the organs involved are the teeth, tongue, gallbladder, salivary glands, liver, and pancreas.
Describe the tissue composition and the general function of each of the four layers of the alimentary canal.
Histology of the Alimentary Canal
•Mucosa is the innermost, moist, epithelial membrane that lines the entire digestive tract. It secretes mucus, digestive enzymes, and hormones; absorbs digestive end products into the blood; and protects against infectious disease.
•Submucosa is a moderately dense connective tissue layer containing blood and lymphatic vessels, lymphoid follicles, and nerve fibers.
•Muscularis externa typically consists of smooth muscle and is responsible for peristalsis and segmentation.
•Serosa, the protective outer layer of the intraperitoneal organs, is the visceral peritoneum.
Describe the composition and functions of saliva, and explain how salivation is regulated.
•Saliva is largely water—97 to 99.5%—and therefore is hypoosmotic. As a rule, saliva is slightly acidic (pH 6.75 to 7.00), but its pH may vary. Its solutes include electrolytes (Na,K,Cl, PO43, and HCO3) the digestive enzymes salivary amylase and lingual lipase (both optimally active at an acid pH); the proteins mucin (mu sin), lysozyme, and IgA; and metabolic wastes (urea and uric acid). When dissolved in water, the glycoprotein mucin forms thick mucus that lubricates the oral cavity and hydrates foodstuffs.
•The intrinsic salivary glands secrete saliva continuously in amounts just sufficient to keep the mouth moist.But when food enters the mouth, the extrinsic glands are activated and copious amounts of saliva pour out. The average output of saliva is 1000–1500 ml per day. Salivation is controlled primarily by the parasympathetic division of the autonomic nervous system.When we ingest foods, chemoreceptors and mechanoreceptors in the mouth send signals to the salivatory nuclei in the brain stem
Explain the dental formula and differentiate clearly between deciduous and permanent teeth.
The dental formula is a shorthand way of indicating the numbers and relative positions of the different types of teeth in the mouth. This formula is written as a ratio, uppers over lowers, for one-half of the mouth.
(2I,1C,2PM,3M)/(2I,1C,2PM,3M) X 2=32 teeth
Primary Dentition consists of the deciduous teeth (decid = falling off), also called milk or baby teeth.
Permanent Teeth enlarge and develop, the roots of the milk teeth are resorbed from below
Describe the mechanisms of chewing and swallowing.
•Mastication, or chewing, begins the mechanical breakdown of food and mixes the food with saliva (p. 866).
•Deglutition, or swallowing, is a complicated process that involves two major phases (p. 866; Fig. 23.13).
1.The buccal phase is voluntary and occurs in the mouth where the bolus is forced into the oropharynx.
2.The pharyngeal-esophageal phase is involuntary and occurs when food is squeezed through the pharynx and into the esophagus.
Identify structural modifications of the wall of the stomach that enhance the digestive process.
Name the cell types responsible for secreting the various components of gastric juice and indicate the importance of each component in stomach activity.
Mucous neck cells, found in the upper, or “neck,” regions of the glands, produce a thin, soluble mucus
Parietal cells - found mainly in the middle region of the glands, simultaneously secrete hydrochloric acid (HCl) and intrinsic factor. Although the parietal cells appear spherical when viewed with a light microscope, they actually have three prongs that bear dense microvilli (they look like fuzzy pitchforks!). This structure provides a huge surface area for secreting H and Cl into the stomach lumen. HCl makes the stomach contents extremely acidic (pH 1.5–3.5), a condition necessary for activation and optimal activity of pepsin. The acidity also helps in food digestion by denaturing proteins and breaking down cell walls of plant foods, and is harsh enough to kill many of the bacteria ingested with foods. Intrinsic factor is a glycoprotein required for vitamin B12 absorption in the small intestine.
Chief cells occur mainly in the basal regions of the gastric glands. The chief cells produce pepsinogen, the inactive form of the protein-digesting enzyme pepsin. Chief cells also secrete insignificant amounts of lipases (fat-digesting enzymes).
Enteroendocrine cells - (“gut endocrine”), typically located deep in the gastric glands, release a variety of chemical messengers directly into the interstitial fluid of the lamina propria.
List the enzymes involved in chemical digestion; name the foodstuffs on which they act.
•salivary amylase - Chemical digestion of carbohydrates begins in the mouth, where salivary amylase breaks large polysaccharides into smaller fragments.
•Pepsin - secreted by the chief cells, begins the chemical digestion of proteins in the stomach.
•Rennin - is produced in infants and breaks down milk proteins.
•Pancreatic enzymes - such as trypsin and chymotrypsin, further break down proteins in the small intestine.
•The brush border enzymes - carboxypeptidase, aminopeptidase, and dipeptidase work on freeing single amino acids in the small intestine.
•Lipases are secreted by the pancreas and are the enzymes that digest fats after they have been pretreated with bile.
List the end products of protein, fat, carbohydrate, and nucleic acid digestion.
oAmino acids are absorbed by cotransport with sodium ions.
oSome dipeptides and tripeptides are absorbed via cotransport with H+ and hydrolyzed to amino acids within the cells.
oAmino acids leave the epithelial cells by facilitated diffusion, enter the capillary blood in the villi, and are transported to the liver via the hepatic portal vein.
oFatty acids and monoglycerides enter the intestinal cells via diffusion.
oFatty acids and monoglycerides are recombined to form triglycerides and then combined with other lipids and proteins within the cells, and the resulting chylomicrons are extruded by exocytosis.
oThe chylomicrons enter the lacteals of the villi and are transported to the systemic circulation via the lymph in the thoracic duct.
oSome short-chain fatty acids are absorbed, move into the capillary blood in the villi by diffusion, and are transported to the liver via the hepatic portal vein.
oMonosaccharides (simple sugars), the monomers of carbohydrates, are absorbed immediately
oGlucose and galactose are absorbed via cotransport with sodium ions.
oFructose passes via facilitated diffusion.
oAll monosaccharides leave the epithelial cells via facilitated diffusion, enter the capillary blood in the villi, and are transported to the liver via the hepatic portal vein.
oUnits enter intestinal cells by active transport via membrane carriers.
oUnits are absorbed into capillary blood in the villi and transported to the liver via the hepatic portal vein.
Describe the gross anatomy of the kidney and its coverings.
•The kidneys are bean-shaped organs that lie retroperitoneal in the superior lumbar region.
•The medial surface is concave and has a renal hilus that leads into a renal sinus, where the blood vessels, nerves, and lymphatics lie.
•The kidneys are surrounded by an outer renal fascia that anchors the kidney and adrenal gland to surrounding structures, a perirenal fat pad that surrounds and cushions the kidney, and a fibrous capsule that prevents surrounding infections from reaching the kidney.
oThere are three distinct regions of the kidney: the cortex, the medulla, and the renal pelvis.
oMajor and minor calyces collect urine and empty it into the renal pelvis.
Trace the blood supply through the kidney.
•Blood supply into and out of the kidneys progresses to the cortex through renal arteries to segmental, lobar, interlobar, arcuate, and cortical radiate arteries, and back to renal veins from cortical radiate, arcuate, and interlobar veins.
•The renal plexus regulates renal blood flow by adjusting the diameter of renal arterioles and influencing the urine-forming role of the nephrons.
Describe the normal physical and chemical properties of urine.
oFreshly voided urine is clear and pale to deep yellow due to urochrome, a pigment resulting from the destruction of hemoglobin.
oFresh urine is slightly aromatic, but develops an ammonia odor if allowed to stand, due to bacterial metabolism of urea.
oUrine is usually slightly acidic (around pH 6) but can vary from about 4.5–8.0 in response to changes in metabolism or diet.
oUrine has a higher specific gravity than water, due to the presence of solutes.
oUrine volume is about 95% water and 5% solutes, the largest solute fraction devoted to the nitrogenous wastes urea, creatinine, and uric acid.
Describe the general location, structure, and function of the ureters.
Describe the general location, structure, and function of the urinary bladder.
•The urinary bladder is a muscular sac that expands as urine is produced by the kidneys to allow storage of urine until voiding is convenient.
•The wall of the bladder has three layers: an outer adventitia, a middle layer of detrusor muscle, and an inner mucosa that is highly folded to allow distention of the bladder without a large increase in internal pressure.
Describe the general location, structure, and function of the urethra.
•The urethra is a muscular tube that drains urine from the body
•There are two sphincter muscles associated with the urethra: the internal urethral sphincter, which is involuntary and formed from detrusor muscle; and the external urethral sphincter, which is voluntary and formed by the skeletal muscle at the urogenital diaphragm.
•The external urethral orifice lies between the clitoris and vaginal opening in females, or occurs at the tip of the penis in males.
Compare the course, length, and functions of the male urethra with those of the female.
•The urethra is 3–4 cm long in females, but closer to 20 cm in males.
•The male urthra has three regions
oProstatic Urethra – about 2.5 cm long, runs within the prostate
oIntermediate part of the Urethra – runs through the urogenital diaphragm, extends 2cm from the prostate to the beginning of the penis
oSpongy Urethra – about 15 long, through the penis and opens at the external urethral orifice
•The male urethra has a double function it carries semen as well as urine out of the body
List the factors that determine body water content and describe the effect of each factor.
•Total body water is a function of age, body mass, and body fat.
•Due to their low body fat and bone mass, infants are about 73% water.
•The body water content of men is about 60%, but because women have relatively more body fat and less skeletal muscle than men, theirs is about 50%.
•Body water declines throughout life, ultimately comprising about 45% of total body mass in old age.
Contrast the overall osmotic effects of electrolytes and nonelectrolytes.
•Nonelectrolytes include most organic molecules, do not dissociate in water, and carry no net electrical charge.
•Electrolytes dissociate in water to ions, and include inorganic salts, acids and bases, and some proteins.
•Electrolytes have greater osmotic power because they dissociate in water and contribute at least two particles to solution.
•The major cation in extracellular fluids is sodium, and the major anion is chloride; in intracellular fluid the major cation is potassium, and the major anion is phosphate.
•Electrolytes are the most abundant solutes in body fluids, but proteins and some nonelectrolytes account for 60–97% of dissolved solutes.
Describe feedback mechanisms that regulate water intake and hormonal controls of water output in urine.
•The thirst mechanism is triggered by a decrease in plasma osmolarity, which results in a dry mouth and excites the hypothalamic thirst center.
•Thirst is quenched as the mucosa of the mouth is moistened, and continues with distention of the stomach and intestines, resulting in inhibition of the hypothalamic thirst center.
•The amount of water reabsorbed in the renal collecting ducts is proportional to ADH release
•When ADH levels are low, most water in the collecting ducts is not reabsorbed, resulting in •When ADH levels are high, filtered water is reabsorbed, resulting in a lower volume of concentrated urine.
•ADH secretion is promoted or inhibited by the hypothalamus in response to changes in solute concentration of extracellular fluid, large changes in blood volume or pressure, or vascular baroreceptors.
Name the three major chemical buffer systems of the body and describe how they resist pH changes.
A chemical buffer is a system of one or two molecules that acts to resist changes in pH by binding H+ when the pH drops, or releasing H+ when the pH rises.1.The bicarbonate buffer system is the main buffer of the extracellular fluid, and consists of carbonic acid and its salt, sodium bicarbonate.
•When a strong acid is added to the solution, carbonic acid is mostly unchanged, but bicarbonate ions of the salt bind excess H+, forming more carbonic acid.
•When a strong base is added to solution, the sodium bicarbonate remains relatively unaffected, but carbonic acid dissociates further, donating more H+ to bind the excess hydroxide.
•Bicarbonate concentration of the extracellular fluid is closely regulated by the kidneys, and plasma bicarbonate concentrations are controlled by the respiratory system.
2.The phosphate buffer system operates in the urine and intracellular fluid similarly to the bicarbonate buffer system: Sodium dihydrogen phosphate is its weak acid, and monohydrogen phosphate is its weak base.
3.The protein buffer system consists of organic acids containing carboxyl groups that dissociate to release H+ when the pH begins to rise, or bind excess H+ when the pH declines.
Describe the influence of the respiratory system on acid-base balance.
Respiratory Regulation of H+
•Carbon dioxide from cellular metabolism enters erythrocytes and is converted to bicarbonate ions for transport in the plasma.
•When hypercapnia occurs, blood pH drops, activating medullary respiratory centers, resulting in increased rate and depth of breathing and increased unloading of CO2 in the lungs.
•When blood pH rises, the respiratory center is depressed, allowing CO2 to accumulate in the blood, lowering pH.
Distinguish between acidosis and alkalosis resulting from respiratory and metabolic factors. Describe the importance of respiratory and renal compensations to acid-base balance.
When arterial blood pH rises above 7.45, the body is in alkalosis; when arterial pH falls below 7.35, the body is in physiological acidosis.
Most hydrogen ions originate as metabolic by-products, although they can also enter the body via ingested foods.
Abnormalities of Acid-Base Balance
•Respiratory acidosis is characterized by falling blood pH and rising PCO2, which can result from shallow breathing or some respiratory diseases.
•Respiratory alkalosis results when carbon dioxide is eliminated from the body faster than it is produced, such as during hyperventilation.
•Metabolic acidosis is characterized by low blood pH and bicarbonate levels, and is due to excessive loss of bicarbonate ions, or ingestion of too much alcohol.
•Metabolic alkalosis is indicated by rising blood pH and bicarbonate levels, and is the result of vomiting or excessive base intake.
•Respiratory rate and depth increase during metabolic acidosis, and decrease during metabolic alkalosis.
•In renal compensation for respiratory acidosis, blood PCO2 and bicarbonate ion concentrations are high; in respiratory alkalosis, blood pH is high, but PCO2 is low.
Describe the structure and function of the testes, and explain the importance of their location in the scrotum.
The testes are the primary reproductive organ of the male, producing both sperm and testosterone.
The testes are divided into lobules with seminiferous tubules inside, where sperm are produced.
Interstitial cells are found in the connective tissue surrounding the seminiferous tubules and produce testosterone.
•The scrotum is a sac of skin and superficial fascia that hangs outside the abdominopelvic cavity at the root of the penis and houses the testes.
It provides an environment 3° below the core body temperature.
oIt responds to temperature changes.
Describe the structure of the penis and indicate its role in the reproductive process.
The penis is the copulatory organ, designed to deliver sperm into the female reproductive tract.
Describe the location, structure, and function of the accessory reproductive organs of the male.
The Male Duct System
•The epididymis consists of a highly coiled tube that provides a place for immature sperm to mature and to be expelled during ejaculation.
•The ductus deferens, or vas deferens, carries sperm from storage sites in the epididymis, through the inguinal canal, over the bladder, and into the ejaculatory duct.
•The urethra is the terminal portion of the male duct system and carries both urine and sperm (not at the same time) to the exterior environment.
•The seminal vesicles lie on the posterior bladder wall and their alkaline secretion accounts for 60% of the volume of semen consisting of fructose, ascorbic acid, a coagulating enzyme (vesiculase), and prostaglandins.
•The prostate gland is responsible for producing a milky, slightly acidic fluid containing citrate, several enzymes, and prostate-specific antigen, making up about one-third of the semen.
•The bulbourethral glands, or Cowper’s glands, produce a thick, clear mucus prior to ejaculation that neutralizes any acidic urine in the urethra.
Describe the phases of the male sexual response.
Define meiosis. Compare and contrast it to mitosis.
Spermatogenesis is the series of events in the seminiferous tubules that produce male gametes (sperm or spermatozoa).
Meiosis consists of two consecutive nuclear divisions and the production of four daughter cells with half as many cells as a normal body cell.
•Meiosis I reduces the number of chromosomes in a cell from 46 to 23 by separating homologous chromosomes into different cells.
•Meiosis II resembles mitosis in every way, except the chromatids are separated into four cells.
Discuss hormonal regulation of testicular function and the physiological effects of testosterone on male reproductive anatomy.
Brain-testicular axis refers to the relationship and interactions between the hypothalamus, anterior pituitary gland, and the testes.
•The hypothalamus releases gonadotropin-releasing hormone (GnRH), which controls the release of the anterior pituitary hormones follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in males.
•FSH indirectly stimulates spermatogenesis.
•LH, also called interstitial cell-stimulating hormone (ICSH), stimulates the interstitial cells to produce testosterone.
•Locally, testosterone acts as a final trigger for spermatogenesis.
•Testosterone inhibits hypothalamic release of GnRH and acts directly on the anterior pituitary gland to inhibit gonadotropin release.
•Inhibin is produced by the sustentacular cells and released when sperm count is high.
Mechanism and Effects of Testosterone Activity
•Testosterone is synthesized from cholesterol and exerts its effects by activating specific genes to be transcribed.
•Testosterone targets accessory organs (ducts, glands, and penis), causing them to grow and assume adult size and function.
•Testosterone induces male secondary sex characteristics: pubic, axillary, and facial hair, deepening of the voice, thickening of the skin and increase in oil production, and an increase in bone and skeletal muscle size and mass.
Describe the location, structure, and function of the ovaries.
The ovaries are the primary reproductive organs of the female.
•The ovaries produce the female gametes (ova, or eggs) and the sex hormones (estrogens and progesterone).
•The paired ovaries are found on either side of the uterus and are held in place by several ligaments.
•Saclike structures called ovarian follicles consist of an immature egg, called an oocyte, encased by one or more layers of different cells.
•Follicles at different stages are distinguished by their structure as primordial follicles, primary follicles, secondary follicles, and Graafian or vesicular follicles.
•Ovulation occurs each month in adult women when one of the maturing follicles ejects its oocyte from the ovary.
•The ruptured follicle transforms into a glandular structure called the corpus luteum, which eventually degenerates.
Describe the location, structure, and function of each of the organs of the female reproductive duct system.
•The uterine tubes, or fallopian tubes or oviducts, form the beginning of the female duct system, receive the ovulated oocyte, and provide a site for fertilization to take place.
•The uterus is a hollow, thick-walled muscular organ that functions to receive, retain, and nourish a fertilized ovum.
•The uterus is supported by the mesometrium, the lateral cervical ligaments, the uterosacral ligaments, and the round ligaments.
•The wall of the uterus is composed of three layers: the perimetrium, the myometrium, and the endometrium.
•The vagina provides a passageway for delivery of an infant and for menstrual blood, and also receives the penis and semen during sexual intercourse.
Describe the anatomy of the female external genitalia.
Discuss the structure and function of the mammary glands.
•Mammary glands are present in both sexes but usually function only in females to produce milk to nourish a newborn baby.
•Mammary glands are modified sweat glands that are really part of the integumentary system.
•Breast cancer usually arises from the epithelial cells of the ducts and grows into a lump in the breast from which cells eventually metastasize.
Describe the process of oogenesis and compare it to spermatogenesis.
Oogenesis is the production of female gametes called oocytes, ova, or eggs.
•A female’s total egg supply is determined at birth and the time in which she releases them extends from puberty to menopause.
•In the fetal period the oogonia multiply rapidly by mitosis, become primordial follicles, and then become primary follicles that begin the first meiotic division.
•After puberty a few oocytes are activated each month, but only one will continue meiosis I, ultimately producing two haploid cells, a polar body, and a secondary oocyte.
•The secondary oocyte stops in metaphase II and if a sperm penetrates it, it will complete meiosis II, producing a second polar body and a large ovum.
Describe the ovarian cycle phases, and relate them to events of oogenesis.
The ovarian cycle is the monthly series of events associated with the maturation of the egg.
1. The follicular phase is the period of follicle growth typically lasting from days 1 to 14.
2. Ovulation occurs when the ovary wall ruptures and the secondary oocyte is expelled.
3. The luteal phase is the period of corpus luteum activity, days 14–28.
Describe the regulation of the ovarian and uterine cycles.
Hormonal Regulation of the Ovarian Cycle
•During childhood, the ovaries grow and secrete small amounts of estrogen that inhibit the release of GnRH until puberty, when the hypothalamus becomes less sensitive to estrogen and begins to release GnRH in a rhythmic manner.
Hormonal Interactions During the Ovarian Cycle
•On day 1 of the cycle, levels of GnRH rise and stimulate increased production and release of FSH and LH.
•FSH and LH stimulate follicle growth and maturation, and estrogen secretion.
•Rising levels of estrogen in the plasma exert negative feedback on the anterior pituitary, inhibiting release of FSH and LH.
•Estrogen exerts positive feedback on the anterior pituitary, resulting in a burst of LH triggering ovulation and transforming the ruptured follicle into the corpus luteum.
•Rising plasma levels of progesterone and estrogen exert negative feedback on LH and FSH release.
•LH levels fall and luteal activity ends; the corpus luteum degenerates, dropping the levels of estrogen and progesterone, and the cycle starts again.
The uterine (menstrual) cycle is a series of cyclic changes that the uterine endometrium goes through each month in response to changing levels of ovarian hormones in the blood
•The menstrual phase takes place on days 1–5 typically, and is the time when the endometrium is shed from the uterus.
•The proliferation phase (days 6–14) is the time in which the endometrium is rebuilt, once again becoming velvety, thick, and well vascularized.
•The secretory phase (days 15–28) is the phase in which the endometrium prepares for implantation of an embryo.