The male reproductive system consists of:-
1.
Two testes
2.
Genital ducts
3.
Male accessory glands
4.
Penis (copulatory organ)
The male reproductive system functions in the formation of spermatozoa, the elaboration of male sex hormones, and the delivery of spermatozoa into female reproductive tract.
Each testis is an oval structure housed in its separate compartment within the scrotum. The testes develop retroperitoneally in the dorsal wall of the abdominal cavity. They migrate during fetal development
&descend into scrotum, where they are suspended at the ends of the spermatic cords. Because of the migration toward the scrotum, each testis carries with it a serous sac, the tunica vaginalis, derived from the peritoneum. The scrotum has an important role in maintaining the testes at a temperature lower than the abdominal temperature. Each testis is surrounded by a thick capsule of dense connective tissue, the tunica albuginea. Outside this is the serous sac, the tunica vaginalis, which partially covers the anterior & lateral surfaces of each testis. The tunica albuginea is thickened on the posterior surface of the testes to form the mediastinum testis, from which fibrous septa penetrate the gland, dividing it into about 250 pyramidal compartments called the testicular lobules. These septa are incomplete, & there is frequently intercommunication between the lobules. Each lobule is occupied by 1-4 seminiferous tubules embedded in the interstitial tissue.
are long convoluted tubules about 150-250
µm in diameter & 30-70 cm long. The combined length of the tubules of
1

one testis is about 250 m. The seminiferous tubules consist of ¹ a tunic of fibrous connective tissue (tunica propria), ² a well-defined basal lamina & ³ a complex germinal or seminiferous epithelium.
The fibrous tunica propria enveloping the seminiferous tubule consists of several layers of fibroblasts. The inner most layer adhering to the basal lamina consists of flattened myoid cells which have characteristics of smooth muscle. Each seminiferous tubule is lined with a complex stratified epithelium. This epithelium consists of 4-8 cell layers & contains ¹Sertoli (supporting cells) & ²Spermatogenic cells.
Sertoli cells: are elongated pyramidal cells. The bases of Sertoli cells adhere to the basal lamina & their apical ends frequently extend into the lumen of the seminiferous tubule. In the L.M., the outlines of Sertoli cells appear poorly defined because of the numerous lateral processes that surround spermatogenic cells. The elongated nucleus, which is often triangular in outline, pale in staining, possesses numerous infoldings & a prominent nucleolus. Studies with the E.M. reveal that these cells contain abundant SER, some RER, a well-developed Golgi complex, numerous mitochondria & lysosomes. Adjacent Sertoli cells are bound together by occluding junctions at the basolateral part of the cell, forming a blood-testis barrier. Sertoli cells are also connected by gap junctions that provide ionic & chemical coupling of the cells.
The functions of Sertoli cells:-
1.
Sertoli cells provide mechanical support, protection & nutritional regulation of the developing spermatozoa. They also seem to play an active role in the release of the mature spermatozoa
(spermiation).
2.
Phagocytosis of the residual bodies (which are left after release of spermatozoa) & also of degenerating germ cells.
3.
Secretion:- aSertoli cells continuously secrete into the seminiferous tubules a fluid that flows in the direction of the genital ducts & is used for sperm transport. bSertoli cells secrete androgen-binding protein (ABP) under the control of the FSH & testosterone & serves to concentrate
2

testosterone in the seminiferous tubule, where it is necessary for spermatogenesis. Sertoli cells can convert testosterone to estradiol. cThey also secrete a peptide called inhibin, which suppresses the synthesis & release of FSH in the anterior pituitary gland.
Sertoli cells produce anti-Müllerian hormone during embryonic life.
This hormone is a glycoprotein that acts during embryonic development to promote regression of the Müllerian (para mesonephric) ducts in the male fetus.
Sertoli cells do not divide during the reproductive period. They are extremely resistant to such adverse conditions as infection, malnutrition
& x-irradiation.
the occluding (tight) junctions between adjacent Sertoli cells are responsible for this barrier & divide seminiferous tubules into a basal compartment containing spermatogonia and adluminal compartment containing the more advanced stages of germ cell differentiation. The blood-testis barrier prevents the entrance of harmful substances from blood into the germinal epithelium of the seminiferous tubules & protects the seminiferous epithelium against autoimmune reaction. Differentiation of spermatogonial cells leads to the appearance of sperm-specific proteins. Since sexual maturity occurs long after the development of the immunocompetence, differentiating germ cells could be recognized as a foreign & provoke an immune response that would destroy the germ cells. Thus, this barrier protects developing germ cells from autoimmune reactions.
Spermatogenic cells: the spermatogenic cells are stacked in 4-8 layers that occupy the space between the basal lamina & the lumen of the tubule. The process of the formation of spermatozoa from spermatogonia is called spermatogenesis which includes the following three phases:-
1.
Spermatocytogenesis (mitosis):- mitotic divisions of the spermatogonia to produce successive generations of cells that finally give rise to primary spermatocytes.
3

2.
Meiosis:-during which the spermatocytes undergo 2 maturation divisions, with reduction by half of the number of chromosomes & amount of DNA producing spermatids.
3.
Spermiogenesis:- during which the spermatids go through an elaborate process of cytodifferentiation, producing spermatozoa.
Spermatogonia: are round cells lying adjacent to the basal lamina. At sexual maturity, spermatogonia begin dividing by mitosis, producing successive generations of cells. Three types of spermatogonia are recognized: type A dark cells, type A pale cells & type B cells. It is thought that type A dark cells are the stem cells, their mitotic division producing more type A dark cells & some type A pale cells, which further replicate by mitosis to form clusters of daughter cells linked to each other by cytoplasmic bridges. Type A pale spermatogonia mature into type B cells, which divide mitotically to produce further type B cells; these cells then mature in a cluster to produce primary spermatocytes.
Primary spermatocytes: are the largest of spermatogenic cells. They are round in shape with large round nucleus, having distinct chromatin network which usually shows the thread-like appearance of cell division.
Soon after their formation, they enter the prophase of the first meiotic division. In this prophase, the cell passes through 4 stages: leptotene, zygotene, pachytene & diplotene. Since the prophase of this division takes about 22 days, the majority of cells seen in sections will be in this phase. Primary spermatocytes replicate their DNA shortly after their formation. It has 46(44+XY) chromosomes &4N of DNA. From this first meiotic division arise smaller cells called secondary spermatocytes.
Secondary spermatocytes: are smaller than primary spermatocytes & have less dense nuclear chromatin with only 23 chromosomes & 2N
DNA. They have short life, (they quickly enter into the second meiotic division) & for that reason they are not usually seen in the seminiferous epithelium. Division of the secondary spermatocytes results in spermatids.
4

Spermatids: are small round cells with small round nucleus with areas of condensed chromatin. They contain 23 chromosomes with 1N DNA.
They are located near the lumen of the seminiferous tubule. Spermatids undergo a complex process of differentiation called spermiogenesis, which includes:
¹ formation of acrosome, ² condensation & elongation of the nucleus, ³ development of the flagellum (tail), & 4 loss of excess of the cytoplasm
(residual bodies).
Spermiogenesis is divided into three phases:-
1.
The Golgi phase
2.
The acrosomal phase
3.
The maturation phase
During the maturation phase, residual cytoplasm is shed & phagocytosed by Sertoli cells & the spermatozoa are released into the lumen of the tubule.
E.M. shows that the majority of divisions of spermatogonia are incomplete regarding the cytoplasm & thus spermatogonia, spermatocytes & spermatids remain connected by cytoplasmic bridges until maturation into spermatozoa.
The intercellular bridges provide communication between the primary
& secondary spermatocytes & spermatids derived from a single spermatogonium. By permitting the interchange of information from cell to cell, these bridges play an important role in coordinating the sequence of events in spermatogenesis. When the process of spermatogenesis is completed, the sloughing of the cytoplasm & cytoplasmic bridges as residual bodies leads to a separation of the late spermatids.
Spermatozoa: the spermatozoon is very elongated (55-65µm) motile cell consists of:-
1.
Flattened head containing the nucleus & acrosomal cap which contains hydrolytic enzymes.
2.
Tail of the spermatozoa composed of:- aNeck:- is a short narrow segment containing the pair of centrioles
& the connecting piece.
5

bMiddle piece:- with an axial axonemal core of microtubules in a cilium-like array (9+2 array of microtubules), nine dense longitudinal fibers, & outermost a sheath of mitochondria ending at the annulus. cPrincipal piece:- which has the same basic ultrastructure as a cilium or flagellum with both longitudinal & circumferential fibres around the axoneme. dEnd piece:- with microtubules like a cilium, but no dense fibers.
The disposition of mitochondria in the middle piece is an example of a concentration of these organelles in sites related to cell movement and high energy consumption.
Movement of the flagellum is a result of the interaction among microtubules, ATP, and dynein, a protein with ATPase activity.
It is characterized by infertility in men because their spermatozoa are immotile. It is due to a lack of dynein or other proteins required for ciliary and flagellar motility in patients spermatozoa. This disorder usually coincides with chronic respiratory infections because of impaired motility of the ciliary axonemes of respiratory epithelium cells.
: fills the spaces between the seminiferous tubules and consists of vascular, very loose connective tissue. Testicular capillaries are fenestrated. The connective tissue consists of various cell types, including fibroblasts, undifferentiated connective tissue cells, mast cells, and macrophages. During puberty, an additional cell type becomes apparent; these are the interstitial or Leydig cells.
Leydig cell: is large rounded or polygonal in shape and has large spherical nucleus, and an eosinophilic cytoplasm`rich in small lipid droplets. Leydig cells occur singly or in clusters and are embedded in the rich plexus of blood and lymph capillaries. Leydig cells have the characteristics of steroid-secreting cells, they produce the male hormone testosterone, which is responsible for the development of male
6

secondary sexual characteristics at puberty and is also essential for the continual function of the seminiferous epithelium. Their cytoplasm contains:
1) Rich SER, which takes the form of anastomosing tubules. SER contains the necessary enzymes to synthesize cholesterol from acetate and other substrates and to transform the pregnenolone produced in the mitochondria into androgens.
2) Numerous spherical or elongated mitochondria contain tubular cristae. The cholesterol side-chain cleaving enzymes are found in mitochondria.
3) Rich in lipid droplets.
4) Well-developed Golgi complex.
Leydig cells also contain Reinke’s crystalloid which is an intracytoplasmic eosinophilic, rod shaped mass, found only in adults, becoming most common in old age, but their function is unknown.
Yellow-brown lipofuscin pigment is present in most Leydig cells.
Both the activity and the number of Leydig cells depend on hormonal stimuli. During human pregnancy, placental gonadotropic hormone passes from the maternal blood to the male fetus, stimulating the abundant fetal testicular interstitial cells that produce androgenic hormones. The presence of these hormones is required for the embryonic differentiation of the male genitalia. The embryonic interstitial cells remain fully differentiated for up to 4 months of gestation; they then regress, with an associated decrease in testosterone synthesis. They remain quiescent throughout the rest of pregnancy and up to the prepubertal period, when they resume testosterone synthesis in response to the stimulus of LH (ICSH) from the hypophysis.
1) Hormones are the factors that have the most important effect on spermatogenesis. Spermatogenesis depends on the action of FSH and LH of the hypophysis on the testicular cells. LH acts on the interstitial cells, stimulating the production of testosterone necessary for the normal development of spermatogenic cells. FSH
7

is known to act on the Sertoli cells, promotes the synthesis and secretion of androgen-binding protein (ABP). This protein combines with testosterone and transports it into the lumen of the seminiferous tubules. Spermatogenesis is stimulated by testosterone and inhibited by estrogen and progesterone.
2) Temperature is very important in the regulation of spermatogenesis which occurs only below the core body temperature of 37 o C.
Testicular temperature is almost 35 o C and is controlled by several mechanisms: a.
A rich venous plexus (the pampiniform plexus) surrounds each testicular artery and forms a countercurrent heat-exchange system that is important in maintaining testicular temperature. b.
Evaportation of sweat from the scrotum, which contributes to heat loss. c.
Contraction of cremaster muscles of the spermatic cords, which pull the testes into the inguinal canals, where their temperature can be increased.
Cryptorchidism (failure of descent of the testes)
Is a developmental defect characterized by failure of the testes to descend into the scrotum. This results in sterility because the temperature of the undescended testes inhibits spermatogenesis. It does not affect testosterone production. This explains why men with cryptorchidism can be sterile but still develop secondary male characteristics and achieve erection. It is associated with a much higher incidence of testicular malignancy than in normally descended testes. It can be surgically corrected.
3) Malnutrition, alcoholism, and the action of certain drugs lead to the alterations in spermatogonia, with a resulting decrease in production of spermatozoa.
X-irradiation and cadmium salts are quite toxic to spermatogenic cells, causing the death of those cells and sterility in animals.
Androgen-producing interstitial cell tumors can cause precocious puberty in males.
8

They are tubuli recti (straight tubules), rete testis, vasa efferentia
(ductuli efferentes), duct of epididymis (ductus epididymidis), vas deferens (ductus deferens), ejaculatory duct, and urethra.
are the tubuli recti, the rete testis, and the ductuli efferentes (vasa efferentia).
Most seminiferous tubules are in the form of loops, both ends of which join the rete testis by tubuli recti . The initial segment of tubuli recti contains only Sertoli cells, followed by a main segment consisting of simple cuboidal epithelium.
Tubuli recti empty into the rete testis , contained within the mediastinum. The rete testis is a highly anastomotic network of channels lined with simple cuboidal epithelium.
From the rete testis extend 10-20 vasa efferentia . They have a wavy lumen. They have an epithelium composed of groups of non-ciliated cuboidal cells alternating with ciliated columnar cells. The non ciliated cells absorb much of the fluid secreted by the seminiferous tubules. The activity of ciliated cells and fluid absorption create a fluid flow that sweeps spermatozoa toward the epididymis. A thin layer of circularly oriented smooth muscle cells is seen outside the basal lamina of the epithelium. The vasa efferentia gradually fuse to form the ductus epididymidis of epididymis.
are the duct of epididymis, the vas deferens, ejaculatory duct, and the urethra.
is a single highly coiled tube about 4-6 meters in length. Together with the surrounding connective tissue and blood vessels, this long canal forms the body and tail of epididymis. It has a large regular lumen. It is lined with pseudostratified columnar epithelium with stereocilia (long branched irregular microvilli). The epithelium is composed of rounded basal cells and columnar cells. These cells are supported on a basal lamina surrounded by smooth muscle
9

cells, whose peristaltic contractions help to move the sperm along the duct. The epithelium of the duct of epididymis participates in the uptake and digestion of residual bodies that are eliminated during spermatogenesis. The major function of the epididymis is the accumulation, storage and maturation of spermatozoa. In the epididymis the spermatozoa develop motility.
is a straight tube with a thick muscular wall. It is the direct continuation of the duct of epididymis. It continues toward the prostatic urethra and empties into it. It has a narrow lumen and a thick layer of smooth muscle. The vas deferens forms part of the spermatic cord, which includes the testicular artery, the pampiniform (venous) plexus, and nerves.
The wall of vas deferens consists of (from inside out):
1) Mucous membrane: its mucosa forms longitudinal folds and is lined along most of its extent by pseudostratified columnar epithelium with stereocilia. The lamina propria is a layer of connective tissue rich in elastic fibers.
2) Thick muscular layer: consists of longitudinal inner and outer layers separated by a circular layer. The abundant smooth muscle produces strong peristaltic contractions that participate in the expulsion of the spermatozoa during ejaculation.
3) Adventitia: composed of connective tissue.
Before it enters the prostate, the ductus deferens dilates, forming a region called the ampulla. In this area, the mucosa becomes thicker and extensively folded. At the final portion of the ampulla, the seminal vesicle joins the duct. From there on, the ductus deferens enters the prostate, opening into the prostatic urethra. The segment entering the prostate is called the ejaculatory duct lined with pseudostratified or simple columnar epithelium.
the male urethra is about 18 cm in length and serves as the terminal portion of both the urinary tract and the reproductive tract. It
10

consists of 3 parts: the prostatic urethra, the membranous urethra, and the penile urethra.
The prostatic urethra: is about 3-4 cm long. It is surrounded by the prostate gland. In this part of the urethra, the ducts of the prostate gland and the ejaculatory ducts open. The prostatic urethra is lined with transitional epithelium.
The membranous urethra : is the narrowest and shortest, measuring about 1 cm in length, lined with stratified or pseudostratified columnar epithelium. It is surrounded by a sphincter of striated muscle, the external sphincter of the urethra.
The Penile urethra : courses through the corpus spongiosum to the external opening of the urethra on the glans penis, it is lined with stratified or pseudostratified columnar epithelium up to the fossa navicularis, then it changes to stratified squamous epithelium to cover the glans penis.
The glands of Littré : are mucous glands found along the entire length of the urethra but mostly in the penile part.
Are the seminal vesicles, the prostate and the bulbourethral glands
(Cowper’s glands).
consists of 2 highly tortuous tubes about 15 cm in length that open into the vas deferens at the junction of ampulla and ejaculatory duct. They are not reservoirs for spermatozoa. They contribute about 2ml of a thick yellowish fluid that is concentrated within the last portion of the ejaculate and contains high concentration of fructose which serves as an energy source for the sperm. Seventy percent 70% of human ejaculate originates from the seminal vesicles.
The wall of the seminal vesicle is composed of:
11

1Extensively folded mucosa: is lined with low pseudostratified columnar epithelium rich in secretory granules. The lamina propria is rich in elastic fibers.
2Muscular layer: is composed of inner circular and outer longitudinal layer of smooth muscle.
3Adventitia: is composed of fibroelastic connective tissue.
The seminal vesicles are glands that produce a viscid, yellowish secretion that contains spermatozoa-activating substances such as fructose, citrate, inositol, prostaglandins, and several proteins.
The height of the epithelial cells of the seminal vesicles and the degree of activity of the secretory processes are dependent on testosterone levels.
is a collection 30-50 branched tubuloalveolar glands whose ducts empty into the prostatic urethra. The prostate is surrounded by a fibroelastic capsule rich in smooth muscle. Septa from this capsule penetrate the gland and divide it into lobes that are indistinct in adult men. The glands are embedded in a fibromuscular stroma.
The prostatic glands are arranged in three zones:
1The transition zone: surrounds the proximal prostatic urethra and comprises about 5% of the glandular tissue. It contains the mucosal glands. It is of medical importance because it is the site where most benign prostatic hyperplasia originates.
2The intermediate central zone: contains the submucosal glands.
3The peripheral zone: forms 70% of the gland, containing the main glands, which is the major site for prostatic cancer.
The epithelium is simple or pseudostratified columnar, lines the individual glands making up the prostate. The main glands contribute most to the volume of the prostatic secretion. The prostatic secretion is a whitish thin fluid containing proteolytic enzymes, citric acid, acid
12

phosphatase, and lipids. The structure and function of the prostate depends on the level of testosterone.
Prostatic concretions (corpora amylacea): are small spherical bodies of glycoproteins 0.2 - 2 mm in diameter, present in the lumen of the glands, and often calcified. Their significance is not understood, but their number increases with age.
are two small glands
(3-5 mm in diameters), located proximal to the membranous portion of the urethra, and empty into it. They are tubuloaveolar glands lined with mucus-secreting simple cuboidal epithelium. Skeletal and smooth muscle cells are present in the septa that divide each gland into lobes.
The secreted mucus is clear and acts as a lubricant for urethra.
the main components of the penis are 3 cylindrical masses of erectile tissue, plus the urethra, surrounded by skin. Two of these cylinders (The corpora cavernosa of the penis) are placed dorsally. The other (The corpus cavernosum of the urethra, or corpus spongiosum) is ventrally located surrounds the urethra. At its end it dilates, forming the glans penis.
The erectile tissue : is composed of cavernous spaces (venous spaces) lined with endothelial cells and separated by trabeculae of connective tissue and smooth muscle (fibromuscular septa or trabeculae).
The corpora cavernosa are covered by a resistant layer of dense connective tissue, the tunica albuginea.
Erection of the penis is due to engorgement of the cavernous spaces with blood under pressure.
The arterial supply of the penis derives from the internal pudendal arteries, which give rise to the deep arteries (central arteries) and the dorsal arteries of the penis. Deep arteries branch to form nutritive and helicine arteries. Nutritive arteries supply oxygen and nutrients to the trabeculae, and helicine arteries empty directly into the cavernous
13

spaces. There are arteriovenous shunts between the helicine arteries and the deep dorsal veins.
Erection occurs when vasodilator impulses of parasympathetic origin cause relaxation of the penile vessels and cavernous smooth m. and closure of arteriovenous shunts. Vasodilatation also involves the concomitant inhibition of sympathetic vasoconstrictor impulses to the penile tissues. Opening of the penile arteries and cavernous spaces account for the increase in the blood flow, the filling of the cavernous spaces, and the resulting rigidity of the penis.
The prepuce : is retractile fold of skin that covers the glans penis.
Consists of spermatozoa together with the fluid (seminal plasma) in which they are suspended. The seminal plasma is a product of the accessory genital glands together with a minor contribution supplied by the genital ducts. The seminal plasma serves as an energy source and vehicle for the spermatozoa.
Semen is a whitish, opaque fluid containing about (50-150) million spermatozoa/1ml. The average volume of the human ejaculate is about 3ml containing 200-300 million sperms.
Semen provides the sperm with transport medium and nutrients, while neutralizing the acidity of the male urethra and vaginal canal, and activating sperm after ejaculation.
is the process by which semen is expelled. The sequence of events includes:
1Lubrication of the urethra by the secretions from bulbourethral and urethral glands.
2Discharge of the prostate.
3Forceful contractions of the ductus epididymidis and ductus deferens to expel the spermatozoa.
4Finally, discharge of the seminal vesicles.
14

15

Testis, rete testis, and vasa efferentia
Vasa efferentia (ductuli efferentes)
16

The highly coiled ductus epididymidis, sectioned several times. Its wall is made of a pseudostratified columnar epithelium surrounded by connective tissue and smooth muscle.
PSH stain. Medium magnification. Inset: Higher magnification of the epithelial cells with their long microvilli (stereocilia).
Low magnification of the Spermatic Cord with the Ductus Deferens (DD)
17

The Ductus Deferens or Vas Deferens
18

Organization of the prostate gland. The prostate secretes and stores a significant contribution to the seminal fluid that is released at ejaculation. It consists of 30–50 branched tubuloalveolar glands organized into three layers, shown here schematically.
Around the prostatic urethra is the transition zone which contains the mucosal glands.
Surrounding most of that zone is the intermediate central zone, which contains the submucosal glands. The outermost and largest layer is the peripheral zone, which contains the most numerous main glands. Glands of all the layers contribute to the prostatic secretion.
Seminal Vesicle
19

Transverse section of the penis
20

The male genital system. The testis and the epididymis are shown in different scales than the other parts of the reproductive system. Note the communication between the testicular lobules.
21

Low magnification of seminiferous tubules and interstitial cells
22

Part of a seminiferous tubule with its surrounding tissues. The seminiferous epithelium is formed by 2 cell populations: the cells of the spermatogenic lineage and the supporting or
Sertoli cells.
23

The Sertoli cells form the blood-testis barrier. Neighbor Sertoli cells are attached by occluding junctions that divide the seminiferous tubules into 2 compartments and impede the passage of substances between both compartments. The basal compartment comprises the interstitial space and the spaces occupied by the spermatogonia. The adluminal compartment comprises the tubule lumen and the intercellular spaces down to the level of the occluding junctions (OJ). In this compartment are spermatocytes, spermatids, and spermatozoa. Cytoplasmic residual bodies from spermatids undergo phagocytosis by the
Sertoli cells and are digested by lysosomal enzymes. The myoid cells surround the seminiferous epithelium.
24

Diagram showing the clonal nature of the germ cells. Only the initial spermatogonia divide and produce separate daughter cells. Once committed to differentiation, the cells of all subsequent divisions stay connected by intercellular cytoplasmic bridges. Only after they are separated from the residual bodies can the spermatozoa be considered isolated cells.
(Modified and reproduced, with permission, from Bloom W, Fawcett DW: A Textbook of
Histology, 10th ed. Saunders, 1975.)
25

Top: The principal changes occurring in spermatids during spermiogenesis. The basic structural feature of the spermatozoon is the head, which consists primarily of condensed nuclear chromatin. The reduced volume of the nucleus affords the sperm greater mobility and may protect the genome from damage while in transit to the egg. The rest of the spermatozoon is structurally arranged to promote motility. Bottom: The structure of a mature spermatozoon
.
26

27

Epithelium of seminiferous tubules surrounded by myoid cells. The spaces between the tubules contain connective tissue, blood and lymphatic vessels, and interstitial cells. PT stain. Medium magnification.
28

Hypophyseal control of male reproduction. Luteinizing hormone (LH) acts on the Leydig cells, and follicle-stimulating hormone (FSH) acts on the seminiferous tubules. A testicular hormone, inhibin, inhibits FSH secretion in the pituitary. ABP, androgen-binding protein.
(Modified and reproduced, with permission, from Bloom W, Fawcett DW: A Textbook of
Histology, 10th ed. Saunders, 1975.)
29