Lab exam 4

Question 1

Describe the location of the kidneys in the body

Answer 1

Kidneys are located along the posterior abdominal wall, lateral to the vertebral column. The left kidney is between the level of the T12 and
L3 vertebrae, and the right kidney is about 2 centimeters inferior to the left kidney to accommodate the large size of the liver. Both kidneys are only partially protected by the rib cage, making them vulnerable to forceful blows to the inferior region of the back.
The kidneys are positioned posterior to the parietal peritoneum in the retroperitoneal space. Thus, only the anterior surface of the kidneys is covered with parietal peritoneum.

Question 2

Identify the structures that compose the urinary system and describe the general function of each

Answer 2

The urinary system is collectively composed of the kidneys, ureters, urinary bladder, and urethra. One of the primary functions of the kidneys is to filter blood and convert the filtrate into urine. This liquid waste is then transported by the ureters from the kidneys to the urinary bladder, which is an expandable, muscular sac that stores as much as 1 liter (L) of urine until it is eliminated from the body through the urethra.

Question 3

List and describe the four tissue layers that surround and support the kidneys

Answer 3

Each kidney is surrounded and supported by several tissue layers. From innermost (closest to the kidney) to outermost, these layers are the fibrous capsule, perinephric fat, renal fascia, and paranephric fat:
∙ The fibrous capsule (or renal capsule) is directly adhered to the external surface of the kidney. It is composed of dense irregular connective tissue and maintains the kidney’s shape, protects it from trauma, and helps prevent infectious pathogens from penetrating
the kidney.
The perinephric fat, also called perirenal fat or adipose capsule, is external to the fibrous capsule and contains adipose connective tissue. It provides cushioning and stabilization for the kidney.
The renal fascia is external to the perinephric fat and is composed of dense irregular connective tissue. It anchors the kidney to surrounding structures.
The paranephric fat, also called pararenal fat or paranephric body, is the outermost layer surrounding the kidney. It is composed of adipose connective tissue and provides cushioning and stabilization for the kidney.

Question 4

Identify and describe the two distinct regions of the kidney and the components of each

Answer 4

The two distinct regions of the parenchyma include an outer renal cortex and an inner renal medulla.
Extensions of the cortex, called renal columns, project into the medulla and subdivide it into renal pyramids (also termed medullary pyramids) that appear striated, or striped. An adult kidney typically contains 8 to 15 renal pyramids. The wide base of a renal pyramid lies at the external edge of the medulla, where it meets the cortex: This is called the corticomedullary junction, or corticomedullary border. The medially directed apex (or tip) of the renal pyramid is called the renal papilla.
The parenchyma of a human kidney can also be divided into 8 to 15 renal lobes. A renal lobe consists of a renal pyramid, portions of renal columns adjacent to either side of the renal pyramid, and the renal cortex external to the pyramid base.

Question 5

Explain the relationship among minor calyces, major calyces, and renal pelvis

Answer 5

Each kidney contains a medially located space called the renal sinus, in addition to the parenchyma. This space serves as the urine drainage area. It is organized into minor calyces, major calyces, and a renal pelvis. Each of the 8 to 15 funnel-shaped minor calyces is associated with a renal pyramid. Several minor calyces merge to form a larger major calyx. Each kidney typically contains two or three major calyces. The major calyces merge to form a large, funnel-shaped renal pelvis. The renal pelvis merges at the medial edge of the kidney with the ureter. Housed within the space around the renal pelvis are the renal artery, renal vein, lymph vessels, and nerves and a variable amount of fat.

Question 6

Explain the autonomic innervation of the kidney

Answer 6

Each kidney is innervated by both divisions of the autonomic nervous system. Sympathetic nerves extend from the T10–T12 segments of the spinal cord to the blood vessels of the kidney, including the afferent and efferent arterioles, as well as innervate the juxtaglomerular apparatus. The general effect of sympathetic stimulation of the kidneys is to decrease urine production. Parasympathetic nerves to the kidney extend from the brain within the vagus nerve (CN X), but the specific effects of parasympathetic innervation to the kidney are not known.

Question 7

Identify and describe a renal corpuscle and its components

Answer 7

The renal corpuscle is an enlarged, bulbous (round) portion of a nephron housed within the renal cortex. It is composed of two structures: the glomerulus and the glomerular capsule.
The glomerulus is a thick tangle of capillary loops called the glomerular capillaries. Blood enters the glomerulus by an afferent arteriole and exits by an efferent arteriole.
The glomerular capsule (Bowman capsule) is formed by two layers: an internal, permeable visceral layer that directly overlies the glomerular capillaries and an external, impermeable parietal layer composed of simple squamous epithelium. Between these two layers is a capsular space that receives the filtrate , which is then modified to form urine.
The renal corpuscle has two opposing poles: a vascular pole and a tubular pole. The vascular pole is where both the afferent and efferent arterioles attach to the glomerulus, and the tubular pole is where the renal tubule originates.

Question 8

Identify and describe the location and structure of the three components of renal tubule

Answer 8

The renal tubule makes up the remaining part of a nephron and is composed of a simple epithelium resting on a basement membrane. It consists of three continuous sections: the proximal convoluted tubule, the nephron loop, and the distal convoluted tubule. The convoluted tubules reside in the cortex, whereas the nephron loop typically extends from the cortex into the medulla.

The proximal convoluted tubule (PCT) is the first region of the renal tubule. It originates at the tubular pole of the renal corpuscle and is composed of a simple cuboidal epithelium with tall, apical microvilli that markedly increase its surface area and thus its reabsorption capacity.
The nephron loop (loop of Henle) originates at a sharp bend in the proximal convoluted tubule. Each nephron loop has two limbs: a descending limb and an ascending limb that are continuous at a “hairpin turn” within the medulla. The descending limb extends medially from the proximal convoluted tubule to the tip of the nephron loop; conversely, the ascending limb of the nephron loop returns to the renal cortex and terminates at the distal convoluted tubule. Portions of both limbs are classified as either thick or thin according to the epithelia composing them.

The distal convoluted tubule (DCT) originates in the renal cortex at the end of the nephron loop’s thick ascending limb and extends to a collecting tubule. Like the proximal convoluted tubule, the distal convoluted tubule is composed of a simple cuboidal epithelium.

Question 9

Name and compare the two types of nephrons and the functional differences between them

Answer 9

The relative position of the renal corpuscle in the cortex and the length of the nephron loop are used to classify nephrons into two categories: cortical nephrons and juxtamedullary nephrons.

Cortical nephrons are oriented with their renal corpuscles near the peripheral edge of the cortex and have a relatively short nephron loop that barely penetrates the medulla. Thus, the bulk of a cortical nephron resides within the cortex. Approximately 85% of nephrons are cortical nephrons.

The remaining 15% of nephrons are called juxtamedullary nephrons. Their renal corpuscles lie adjacent to the corticomedullary junction, and they have relatively long nephron loops that extend deep into the medulla. Juxtamedullary nephrons are important in establishing a salt concentration gradient within the interstitial space that lies outside the nephron loop, the collecting tubules, and the collecting ducts—thus allowing for the regulation of urine concentration by antidiuretic hormone (ADH)

Question 10

Explain the relationship between collecting tubules and collecting ducts

Answer 10

Several nephrons drain into each collecting tubule. Each kidney contains thousands of collecting tubules, and a series of collecting tubules empty into larger collecting ducts. Both collecting tubules and collecting ducts project through the renal medulla toward the renal papilla. Numerous collecting ducts then empty into a papillary duct located within the renal papilla. Papillary ducts are the most distal portion of the collecting ducts and empty into a minor calyx.

Question 11

Identify the location and describe the structure of the juxtaglomerular apparatus

Answer 11

With the nephron in the normal orientation, there is physical contact between the afferent arteriole and the adjacent distal convoluted tubule (DCT) forming the juxtaglomerular apparatus. The primary components of the JG apparatus include both granular cells and macula densa cells. Granular cells (or juxtaglomerular cells) are modified smooth muscle cells of the afferent arteriole located near its entrance into the renal corpuscle. Granular cells have two functions: (1) They contract when stimulated either by stretch or by the sympathetic division of the autonomic nervous system, and (2) they synthesize, store, and release the enzyme renin. Renin is required in the production of angiotensin I, which is then converted by angiotensin-converting enzyme (ACE) to angiotensin II

Question 12

Explain the functions of both granular cells and cells of the macula densa

Answer 12

Granular cells (or juxtaglomerular cells) are modified smooth muscle cells of the afferent arteriole located near its entrance into the renal corpuscle. Granular cells have two functions: (1) They contract when stimulated either by stretch or by the sympathetic division of the autonomic nervous system, and (2) they synthesize, store, and release the enzyme renin. Renin is required in the production of angiotensin I, which is then converted by angiotensin-converting enzyme (ACE) to angiotensin II.

The macula densa is a group of modified epithelial cells in the wall of the distal convoluted tubule where it contacts the granular cells. The cells of the macula densa are located only in the tubule wall adjacent to the granular cells of the afferent arteriole, and they are narrower and taller than other distal convoluted tubule epithelial cells. The macula densa cells detect changes in the sodium chloride (NaCl) concentration of fluid within the lumen of the distal convoluted tubule. Macula densa cells signal granular cells in the afferent arteriole to release renin through paracrine stimulation

Question 13

List the series of blood vessels for the path of blood flow into and out of the kidney

Answer 13

Blood is delivered to each kidney by way of a renal artery that arises from the abdominal aorta. The renal artery branches as it enters the renal sinus into segmental arteries. While still in the renal sinus, the segmental arteries branch to form the interlobar arteries, which are located between the renal lobes. The interlobar arteries extend to the corticomedullary junction, where they branch to form arcuate arteries. Arcuate arteries are arch-shaped and project parallel to the base of the medullary pyramid at the corticomedullary junction. The arcuate arteries extend branches called interlobular arteries (or cortical radiate arteries) that project peripherally into the cortex (where renal lobules are located). As the interlobular arteries extend into the cortex, numerous small afferent arterioles branch from them.

Blood drains from both peritubular and vasa recta capillary beds into small veins. The smallest of these veins are the interlobular veins. Interlobular veins merge to form arcuate veins at the base of the medullary pyramids, and these merge to form interlobar veins, which extend through the renal columns. Interlobar veins merge in the renal sinus to form the renal vein. Note that there are no segmental veins; rather, the interlobar veins directly form the renal vein. The renal vein leaves the kidney at its hilum and drains into the inferior vena cava.

Question 14

Identify the three different capillaries within the kidney and describe the function of each as the
site of either the filtration of blood or the exchange of gases and nutrients

Answer 14

Each afferent arteriole supplies blood to a glomerulus. Some blood plasma is filtered at the glomerulus (this fluid enters the glomerular capsule of the renal corpuscle). After this filtration event, most blood (which was unfiltered and remains within the glomerulus) exits the glomerulus through an efferent arteriole. Each efferent arteriole now branches into a second capillary network, either the peritubular capillaries or vasa recta. The peritubular capillaries are associated with, and intertwined around, both the proximal and distal convoluted tubules; thus, they primarily reside in the cortex of the kidney. In comparison, vasa recta capillaries are “straight vessels” associated with the nephron loop; thus, they primarily reside in the medulla of the kidney.
Notice that all blood moves through two capillary beds as it flows through the kidney. Blood first enters from the afferent arteriole into the glomerular capillaries, where it is filtered. When the blood reaches the second capillary bed of either the peritubular capillaries or the vasa recta, the exchange of gases, nutrients, and wastes occurs between the tissues of the kidney and the blood. The peritubular capillaries and vasa recta then drain into the network of veins.

Question 15

Differentiate among filtrate, tubular fluid, and urine, and list the urinary system structures that transport each of these fluids

Answer 15

When blood flows through the glomerulus and is filtered, both water and solutes move from the blood plasma across the filtration membrane and into the capsular space to form filtrate. This filtrate then enters the proximal convoluted tubule. where it is now called tubular fluid. It flows through the proximal convoluted tubule, nephron loop, and distal convoluted tubule. Tubular fluid from several distal convoluted tubules enters into small collecting tubules that empty into larger collecting ducts.
Tubular fluid is not changed further after leaving the collecting ducts, and it is now called urine. It enters a papillary duct located within a renal papilla and then flows progressively through spaces within the renal sinus of the kidney.

Question 16

Trace the fluid from its formation at the renal corpuscle until it exits the body through the urethra

Answer 16

When blood flows through the glomerulus and is filtered, both water and solutes move from the blood plasma across the filtration membrane and into the capsular space to form filtrate. This filtrate then enters the proximal convoluted tubule. where it is now called tubular fluid. It flows through the proximal convoluted tubule, nephron loop, and distal convoluted tubule. Tubular fluid from several distal convoluted tubules enters into small collecting tubules that empty into larger collecting ducts.
Tubular fluid is not changed further after leaving the collecting ducts, and it is now called urine. It enters a papillary duct located within a renal papilla and then flows progressively through spaces within the renal sinus of the kidney. These spaces occur in the follow- ing order: minor calyx, major calyx, and renal pelvis. The renal pelvis transports urine from the kidney into a ureter, and a ureter from each kidney transports urine into the urinary bladder, where it is stored until it is excreted from the body through the urethra.

Question 17

Describe the structure of urinary bladder

Answer 17

The bladder is positioned immediately posterior to the pubic symphysis. In females, the urinary bladder is anteroinferior to the uterus and directly anterior to the vagina; in males, the bladder is anterior to the rectum and superior to the prostate gland. The urinary bladder is a retroperitoneal organ, and only its superior surface is covered with the parietal peritoneum. When it is empty, the urinary bladder exhibits an inverted pyramidal shape. As it fills, the bladder distends superiorly until it assumes an oval shape.

A posteroinferior triangular area of the urinary bladder wall, called the trigone, is formed by imaginary lines connecting the two ureter openings and the urethral opening. The trigone remains immobile as the urinary bladder fills and evacuates. It functions as a funnel to direct urine into the urethra as the bladder wall contracts to eliminate the stored urine.
The four tunics that form the wall of the bladder are the mucosa, submucosa, muscularis, and adventitia. The innermost mucosa is formed by a transitional epithelium, which accommodates the shape changes occurring with distension, and by a highly vascularized lamina propria that supports the mucosa. Additionally, mucosal folds, or rugae, allow for even greater distension. Within the trigone region, the mucosa is smooth, thick, and lacking mucosal folds. The submucosa lies immediately external to the mucosa and is formed by dense irregular connective tissue that supports the urinary bladder wall.
The muscularis is formed by three layers of smooth muscle, collectively called the detrusor muscle. At the neck of the urinary bladder, an involuntary internal urethral sphincter is formed by the smooth muscle that encircles the urethral opening.
The adventitia is the outer layer of areolar connective tissue covering the urinary bladder. A peritoneal membrane covers only the superior surface of the urinary bladder.

Question 18

Compare and contrast the female urethra and male urethra

Answer 18

The female urethra has a single function: to transport urine from the urinary bladder to exterior of the body. The lumen of the female urethra is primarily lined with a stratified squamous epithelium. The urethra is approximately 4 centimeters (about 1.6 inches) long, and it opens to the outside of the body at the external urethral orifice located in the female perineum.

The male urethra has both urinary and reproductive functions because it serves as a passageway for both urine and semen (but not at the same time). It is approximately 19 centimeters long and is partitioned into three segments: the prostatic urethra, the membranous urethra, and the spongy urethra.
The prostatic urethra is the most dilatable portion of the urethra. It extends through the prostate gland immediately inferior to the male bladder, where multiple small prostatic ducts enter it. Two smooth muscle bundles surround the mucosa: an internal longitudinal bundle and an external circular bundle. The external, circular muscular bundles are a continuation of the thickened, circular region of the internal urethral sphincter at the bladder outlet. The membranous urethra is the shortest and least dilatable portion of the male urethra. It extends from the inferior surface of the prostate gland through the urogenital diaphragm.
The spongy urethra (or penile urethra) is the longest part of the male urethra at approximately 15 centimeters long (about 6 inches). It is encased within a cylinder of erectile tissue in the penis called the corpus spongiosum, and it extends to the external urethral orifice.

Question 19

Describe the abnormal constituents of urine and their possible causes

Answer 19

Glucose: Diabetes mellitus

Ketones (acetone, acetoacetic acid, beta-hydroxybutyric acid): Diabetes mellitus, starvation, low-carbohydrate diet; ketones produced as by-products of fatty acid metabolism

Protein: Increased glomerular permeability caused by kidney trauma, heavy metals, bacterial toxins, exertion, hypertension, cold exposure, glomerular nephritis

Bile pigment: Liver pathology (e.g., hepatitis, cirrhosis), obstructed bile duct due to gallstones

Erythrocytes: Glomerular damage, kidney trauma, pathology along the urinary tract, contamination from menstrual flow

Hemoglobin (Hb): Accelerated rate of erythrocyte destruction (e.g., hemolytic anemia, a transfusion reaction), burns, renal damage, contamination from menstrual flow

Leukocytes: Urinary tract infection, acute glomerulonephritis, contamination from female reproductive tract

Nitrates: Urinary tract infection because bacteria convert nitrates (NO3-) to nitrites (NO2-)

Myoglobin: Rhabdomyolysis (a condition where skeletal muscle breaks down; caused by excessive exercise and is an uncommon side effect of statins)

Question 20

List the similarities between the female and male reproductive systems

Answer 20

Both females and males have paired primary reproductive organs called gonads: These are ovaries in females and testes in males. The gonads produce sex cells called gametes. Gametes are oocytes in females and sperm in males, which unite at fertilization to initiate the formation of a new individual.
∙ The gonads also produce relatively large amounts of sex hormones, which affect maturation, development, and changes in the activity of the reproductive system organs.
∙ Both sexes also have accessory reproductive organs, including ducts to carry gametes away from the gonads toward the site of fertilization (in females) or to the outside of the body (in males).

Ovary/Testis: Produces gametes and sex hormones

Clitoris/Glans of penis: Contains erectile tissue that is stimulated during sexual arousal and orgasm

Labia minora/Body of penis: Contains erectile tissue that is stimulated during sexual arousal and orgasm

Labia majora/Scrotum: Protect and cover some reproductive structures

Greater vestibular gland/Bulbourethral gland: Secretes mucin for lubrication

Question 21

Identify the hormones responsible for initiating puberty (sexual maturation)

Answer 21

Puberty is initiated when the hypothalamus begins secreting gonadotropin-releasing hormone (GnRH). GnRH acts on specific endocrine cells in the anterior pituitary and stimulates them to release the gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH). (Prior to puberty, FSH and LH are virtually nonexistent in girls and boys.) As levels of FSH and LH increase, the gonads produce significant levels of sex hormones and start the processes of both gamete and sexual maturation.

Question 22

Compare the components of the perineum between females and males

Answer 22

In both females and males, the perineum is the diamond-shaped area between the thighs, extending from the pubis anteriorly to the coccyx posteriorly, and bordered laterally by the ischial tuberosities.

Two distinct triangle bases are formed by an imaginary horizontal line extending between the ischial tuberosities of the ossa coxae.

∙ The anterior triangle, called the urogenital triangle, contains the urethral and vaginal orifices in females and the base of the penis and the scrotum in males. Within the urogenital triangle are the muscles that surround the external genitalia, called the ischiocavernosus, bulbospongiosus, and superficial transverse perineal muscles.

∙ The posterior triangle, called the anal triangle, is the location of the anus in both sexes. Surrounding the anus is the external anal sphincter.
The external anal sphincter, bulbospongiosus, and superficial transverse perineal muscles are partly anchored by a dense connective tissue structure called the perineal body.

Question 23

Describe the gross and microscopic anatomy of the ovary

Answer 23

The ovaries are anchored within the pelvic cavity by specific cords and sheets of connective tissue. A double fold of peritoneum, called the mesovarium, attaches to each ovary at its hilum, which is the anterior surface of the ovary where its blood vessels and nerves enter and leave the organ. The mesovarium secures each ovary to a broad ligament, which is a drape of peritoneum that hangs over the uterus. (Specifically, the mesovarium attaches to the mesosalpinx portion of the broad ligament.) Each ovary is anchored to the lateral wall of the uterus by an ovarian ligament. Finally, a suspensory ligament attaches to the lateral edge of each ovary and projects superolaterally to the pelvic wall. The ovarian blood vessels and nerves are housed within each suspensory ligament, and they join the ovary at its hilum.

Surrounding the ovary is a thin, simple cuboidal epithelial layer called the germinal epithelium, so named because early anatomists erroneously thought it was the origin of the female germ (sex) cells. Deep to the germinal epithelium is a dense connective tissue capsule called the tunica albuginea. Deep to the tunica albuginea, the ovary can be partitioned into an outer cortex and an inner medulla. The cortex contains connective tissue and ovarian follicles, whereas the medulla is composed of areolar connective tissue and contains branches of the ovarian blood vessels, lymph vessels, and nerves.

Question 24

Compare the different types of ovarian follicles that form in the ovary

Answer 24

Within the cortex are thousands of ovarian follicles. Ovarian follicles consist of an oocyte surrounded by follicle cells (or granulosa cells), which support the oocyte. There are several different types of ovarian follicles, each representing a different stage of development:

Primordial follicle: (Primary oocyte) Single layer of flattened follicular cells surround an oocyte during Fetal period

Primary follicle: (Primary oocyte) Single layer of cuboidal granulosa cells surround an oocyte during puberty

Secondary follicle: (Primary oocyte) Multiple layers of granulosa cells surround the oocyte during Puberty

Antral follicle: (Primary oocyte) Many layers of granulosa cells surround the oocyte and a small antrum develops within layers of granulosa cells during Puberty

Mature follicle: (Secondary oocyte)
Many layers of granulosa cells surround the oocyte and a very large antrum during Puberty

Corpus luteum: (No oocyte)
Yellowish, collapsed folds of granulosa cells during Puberty

Corpus albicans: (No oocyte)
Whitish connective tissue scar, remnant of a degenerated corpus luteum during Puberty

Question 25

Describe the anatomy and function of the uterine tubes

Answer 25

The uterine tubes, also called the fallopian tubes or oviducts, extend laterally from both sides of the uterus toward the ovaries. They function to trans- port the ovulated oocyte to the uterus, and are the site of fertilization of an oocyte. These tubes are covered and suspended by the mesosalpinx, a specific superior part of the broad ligament of the uterus. Each uterine tube is composed of the following contiguous segments:
∙ The infundibulum is the free, funnel-shaped, lateral margin of the uterine tube. Its numerous fingerlike folds are called fimbriae. The fimbriae of the infundibulum envelop the ovary only at the time of ovulation.
∙ The ampulla is the expanded region medial to the infundibulum. Fertilization of an oocyte typically occurs there.
∙ The isthmus is the constricted region that extends medially from the ampulla toward the lateral wall of the uterus. It forms about one-third of the length of the uterine tube.
∙ The uterine part is also called the intramural part or interstitial segment, and it extends medially from the isthmus and penetrates the wall of the uterus.
The wall of the uterine tube consists of a mucosa, a muscularis, and a serosa. The mucosa is formed from a simple ciliated columnar epithelium and an underlying layer of areolar connective tissue. After ovulation, the cilia on the apical surface of the epithelial cells of both the infundibulum and the ampulla begin to beat in the direction of the uterus. This causes a slight current in the fluid within the uterine tube lumen, drawing the oocyte into the uterine tube and moving it toward the uterus.
The muscularis is composed of an inner circular layer and an outer longitudinal layer of smooth muscle. Some peristaltic contractions in the muscularis help propel the oocyte, or pre-embryo if fertilization has occurred, through the uterine tube toward the uterus. Thus, oocyte movement through the uterine tubes is facilitated by both cilia movement and peristaltic contractions. The serosa is composed of a thin layer of areolar connective tissue and an external serous membrane covering the uterine tube.

Question 26

List the functions of the uterus and compare its three tunics

Answer 26

Following fertilization, the pre-embryo makes contact with the uterine lining and implants in the inner uterine wall. The uterus then supports, protects, and nourishes the developing embryo/fetus by forming a vascular connection that later develops into the placenta. The uterus ejects the fetus at birth after maternal oxytocin levels increase to initiate the uterine contractions of labor. If an oocyte is not fertilized, the muscular wall of the uterus contracts and sheds its inner lining as menstruation.

The uterine wall is composed of three concentric tunics: the perimetrium, myometrium, and endometrium. The outer tunic is a serosa called the perimetrium. The perimetrium is continuous with the broad ligament. The myometrium is the thick, middle tunic of the uterine wall formed from three intertwining layers of smooth muscle. The innermost tunic of the uterus, called the endometrium, is an intricate mucosa composed of a simple columnar epithelium and an underlying lamina propria. The lamina propria is filled with compound tubular glands (also called uterine glands), which enlarge during the uterine cycle.
Two distinct layers form the endometrium. The deeper layer is the basal layer, also called the stratum basalis. The basal layer is immediately adjacent to the myometrium and is a permanent layer that undergoes few changes during each uterine cycle.
The more superficial of the two endometrial layers is the functional layer, or stratum functionalis. Beginning at puberty, the functional layer grows from the basal layer under the influence of estrogen and progesterone secreted from the ovarian follicles. If fertilization and implantation do not occur, the functional layer is shed as menses. The basal layer gives rise to a new functional layer after the end of each menses.

Question 27

Describe the components of the female external genitalia

Answer 27

The mons pubis is an expanse of skin and subcutaneous connective tissue immediately anterior to the pubic symphysis. The mons pubis is covered with pubic hair in postpubescent females. The labia majora are paired, thickened folds of skin and connective tissue. The labia majora are homologous to the scrotum of the male. In adulthood, their outer surface is covered with coarse pubic hair; they contain numerous sweat and sebaceous glands. The labia minora are paired folds immediately internal to the labia majora. They are devoid of hair and contain a highly vascular layer of areolar connective tissue. Sebaceous glands are located within these folds, as are numerous melanocytes, resulting in enhanced pigmentation of the folds.

The space between the labia minora is called the vestibule. Within the vestibule are the urethral opening and the vaginal orifice. On either side of the vaginal orifice is an erectile body called the bulb of the vestibule, which engorges with blood and increases in sensitivity during sexual intercourse. A pair of greater vestibular glands (previously called glands of Bartholin) are housed within the posterolateral walls of the vestibule and secrete mucin, which forms mucus to act as a lubricant for the vagina. Secretion increases during sexual intercourse, when additional lubrication is needed.
The clitoris is a small erectile body, usually less than 2 centimeters in length, located at the anterior regions of the labia minora. It is homologous to the penis of the male. Two small erectile bodies called corpora cavernosa form the body of the clitoris. The corpora cavernosa become engorged with blood and increase in sensitivity during sexual intercourse. Extending from each of these bodies posteriorly are elongated masses, each called
the crus of the clitoris, which attach to the pubic arch. Capping the body of the clitoris is the glans. The prepuce is an external fold of the labia minora that forms a hoodlike covering over the clitoris.

Question 28

Describe the anatomy of the mammary glands

Answer 28

Each mammary gland, or breast, is located within the anterior thoracic wall and is composed of a compound tubuloalveolar exocrine gland. The gland’s secretory product is called breast milk and it contains proteins, fats, and lactose sugar to provide nutrition to infants.
The nipple is a cylindrical projection on the center of the mammary gland. It contains multiple, tiny openings of the excretory ducts that transport breast milk. The areola is the pigmented, rosy or brownish ring of skin around the nipple. Its surface often appears uneven and grainy due to the numerous sebaceous glands, called areolar glands, immediately internal to the surface. The color of the areola may vary, depending upon whether or not a woman has given birth. In a nulliparous woman, one who has never given birth, the areola is rosy or light brown in color. In a parous woman, one who has given birth, the areola may change to a darker color.
Internally, the mammary glands are supported by fibrous connective bands called suspensory ligaments. These thin bands extend from the skin and attach to the deep fascia overlying the pectoralis major muscle. Thus, the mammary gland and the pectoralis major muscle are structurally linked.
The mammary glands are subdivided into lobes, which are further subdivided into smaller compartments called lobules. Lobules contain secretory units termed alveoli that produce milk in the lactating female. Alveoli become more numerous and larger during pregnancy. Tiny ducts drain milk from the alveoli and lobules. The tiny ducts of the lobules merge and form 10 to 20 larger channels called lactiferous ducts. A lactiferous duct drains breast milk from a single lobe. As each lactiferous duct approaches the nipple, its lumen expands to form a lactiferous sinus, a space where milk is stored prior to release from the nipple.
Breast milk is released by a process called lactation, which occurs in response to a complex sequence of internal and external stimuli.

Question 29

Identify and describe the gross anatomy and function of the scrotum

Answer 29

The scrotum, a skin-covered sac between the thighs, provides the cooler environment needed for normal sperm development and maturation. Embryologically, the scrotum is homologous to the labia majora in the female.
Externally, the scrotum contains a distinct, ridgelike seam at its midline, called the raphe. The raphe extends in an anterior direction along the inferior surface of the penis and in a posterior direction to the anus. The wall of the scrotum is composed of an external layer of skin, a thin layer of superficial fascia immediately internal to the skin, and a layer of smooth muscle, the dartos muscle, immediately internal to the fascia.
The blood vessels and nerves supplying each testis extend from within the abdomen to the scrotum in a multilayered structure called the spermatic cord. The spermatic cord originates in the inguinal canal, a tubelike passageway through the inferior abdominal wall. The spermatic cord wall consists of three layers:
∙ An external spermatic fascia is formed from the aponeurosis of the external oblique muscle.
∙ The cremaster muscle and cremasteric fascia are formed from muscle fiber extensions of the internal oblique muscle and its aponeurosis, respectively.
∙ An internal spermatic fascia is formed from fascia deep to the abdominal muscles.
Within the spermatic cord is a singular testicular artery that is a direct branch from the abdominal aorta. The testicular artery is surrounded by a plexus of veins called the pampiniform plexus.

Question 30

Describe the gross anatomy and microscopic anatomy of the testes

Answer 30

Each testis is covered anteriorly and laterally by a serous membrane, the tunica vaginalis. This membrane is derived from the peritoneum of the abdominal cavity. The tunica vaginalis has an outer parietal layer and an inner visceral layer that are separated by a cavity filled with serous fluid. A thick, whitish, fibrous capsule called the tunica albuginea covers the testis and lies immediately deep to the visceral layer of the tunica vaginalis. At the posterior margin of the testis, the tunica albuginea thickens and projects into the interior of the organ as the mediastinum testis. Blood vessels, a system of ducts, within lymph vessels, and some nerves enter or leave each testis within the mediastinum testis.
The tunica albuginea projects internally into the testis and forms delicate connective tissue septa, which subdivide the internal space into about 250 separate lobules. Each lobule contains up to four extremely convoluted, thin, and elongated seminiferous tubules. The seminiferous tubules contain two types of cells: (1) a group of nondividing support cells called the sustentacular cells, which also are termed Sertoli cells, or nurse cells; and (2) a population of dividing germ cells that continuously replicate and develop into sperm beginning at puberty.
The sustentacular cells provide a protective environment for the developing sperm, and their cytoplasm helps nourish the developing sperm. In addition, sustentacular cells release the hormone inhibin when sperm count is high. Inhibin inhibits FSH secretion and thus regulates sperm production. Conversely, when sperm count declines, inhibin secretion decreases.
The sustentacular cells are bound together by tight junctions, which form a blood-testis barrier that is similar to the blood-brain barrier.

Question 31

Explain the function of each component of the ducts associated with the male reproductive
system

Answer 31

The rete testis is a meshwork of interconnected channels in the mediastinum testis that receive sperm from the seminiferous tubules via straight tubules. The rete testis is lined by simple cuboidal epithelium with short microvilli covering its luminal surface. The channels of the rete testis merge to form the efferent ductules.
Approximately 12 to 15 efferent ductules connect the rete testis to the epididymis. They are lined with both ciliated columnar epithelia that propel the sperm toward the epididymis and nonciliated columnar epithelia that absorb excess fluid secreted by the seminiferous tubules. The efferent ductules provide passage for the sperm from the rete testis into the epididymis.

The epididymis stores sperm until they are fully mature and capable of being motile. When sperm leave the epididymis during ejaculation, they enter the ductus deferens, also called the vas deferens. The ejaculatory duct conducts sperm (from the ductus deferens) and a component of seminal fluid (from the seminal vesicle) into the prostatic urethra.

Question 32

Trace the pathway that sperm travel through the testes and duct system

Answer 32

Formed in testes. Mature in the epididymis. Then passes through the vas deferens, then through the ejaculatory duct into the prostatic urethra, then through the intermediate urethra, then through the spongy urethra and finally to the body exterior.

Question 33

Describe the anatomy and function of the accessory glands

Answer 33

The paired seminal vesicles are located on the posterior surface of the urinary bladder lateral to the ampulla of the ductus deferens. Each seminal vesicle is an elongated, hollow organ approximately 5 to 8 centimeters long. The wall of each vesicle contains mucosal folds of pseudostratified columnar epithelium. The medial portion of the seminal vesicle merges with a ductus deferens to form the ejaculatory duct.
The seminal vesicles secrete a viscous, whitish-yellow, alkaline fluid containing both fructose and high levels of prostaglandins. Fructose nourishes the sperm as they travel through the female reproductive tract. Prostaglandins are hormonelike sub- stances that promote the widening and slight dilation of the external os of the cervix, which facilitates sperm entry into the uterus. Prostaglandins also promote smooth muscle contraction of the uterus.

The prostate gland is a compact, encapsulated organ that weighs about 20 grams and is shaped like a walnut, measuring approximately 2 cm by 3 cm by 4 cm. It is located immediately inferior to the bladder. The prostate gland includes submucosal glands that produce mucin and more than 30 tubuloalveolar glands that open directly through numerous ducts into the prostatic urethra

Paired, pea-shaped bulbourethral glands (or Cowper glands) are located within the urogenital diaphragm on each side of the membranous urethra. Each gland has a short duct that projects into the bulb (base) of the penis and enters the spongy urethra. Bulbourethral glands are tubuloalveolar glands that have a simple columnar and pseudostratified columnar epithelium. Their secretory product is a clear, viscous mucin that forms mucus. This mucus coats and lubricates the urethra for the passage of sperm during sexual intercourse.

Question 34

Compare and contrast sperm, seminal fluid, and semen

Answer 34

Sperm cannot survive in this type of environment, so an alkaline secretion called seminal fluid is needed to neutralize the acidity of the vagina.

Seminal fluid from the accessory glands combines with sperm from the testes to make up semen