The Histology of Female Genital System Semester VI (2012)

Contents :
Female Reproductive System
Ovaries
Ovarian Follicles
Uterus
Menstrual Cycle
Mammary Gland


Female Reproductive System

The female reproductive system consists of the internal reproductive organs (the paired ovaries and oviducts, the uterus, and the vagina) and the external genitalia.

Although the mammary glands are not considered part of the female reproductive system, their physiology and function are so closely associated with the reproductive system.

Ovaries

The paired ovaries, located within the pelvis, are almond-shaped bodies 3 cm long, 1.5 to 2 cm wide, and 1 cm thick.

The surface epithelium covering the ovaries, called the germinal epithelium, is a modified peritoneum. Directly beneath this epithelium is the tunica albuginea, the connective tissue capsule whose collagen fibers are oriented parallel to the ovary surface.

Each ovary is subdivided into the highly cellular cortex and a medulla.

The ovarian cortex is composed of a connective tissue framework, the stroma, housing fibroblast-like stromal cells as well as ovarian follicles in various stages of development. The medulla contains large blood vessels, lymph vessels, and nerve fibers embedded in a connective tissue stroma.

Before the onset of puberty, all of the follicles of the ovarian cortex are in the primordial follicle stage. The pulsatile release of GnRH from the hypothalamus results in a similar, pulsatile, release of gonadotropins (follicle-stimulating hormone [FSH], and leutinizing hormone [LH]) from the basophils of the anterior pituitary that culminates in the commencement of follicular development and the onset of the ovulatory cycle.

The development of the primary follicles is independent of FSH; differentiation and proliferation of the follicular cells are triggered by local factors secreted by cells of the ovary. Secondary and later follicles, however, are under the influence of FSH. Follicular development usually culminates in the release of a single oocyte (ovulation).

Ovarian Follicles

Ovarian follicles are surrounded by stromal tissue and consist of a primary oocyte and its associated follicular cells arranged in a single spherical layer or several concentric layers around the primary oocyte.

There are four identifiable stages of follicular development based on the growth of the follicle and the development of the oocyte: Primordial follicles, unilaminar and multilaminar primary follicles, secondary (antral) follicles, and Graafian (mature) follicles.

The development of the primordial and primary follicles is independent of FSH; instead, the differentiation and proliferation of the follicular cells are triggered by as yet uncharacterized local factors secreted by cells of the ovary. Secondary and later follicles, however, are under the influence of FSH. Follicular development usually culminates in the release of a single oocyte (ovulation).

Primordial follicles, the most primitive follicles, are abundant before birth, after which they become fewer in number. The primordial follicle is composed of a primary oocyte, arrested in the prophase stage of meiosis I, is surrounded by a single layer of flattened follicular cells.

Primary Follicle

Primordial follicles develop into primary follicles distinguished as a result of changes in the primary oocyte, the follicular cells, and the surrounding stromal tissue.

The primary oocyte grows to about 100 to 150 μm in diameter with an enlarged nucleus (sometimes called the germinal vesicle).

Follicular cells become cuboidal in shape. As long as only a single layer of follicular cells encircles the oocyte, the follicle is called a unilaminar primary follicle. When the follicular cells proliferate and stratify, forming several layers of cells around the primary oocyte, the follicle is called a multilaminar primary follicle, and the follicular cells are more commonly referred to as granulosa cells.

During this stage, an amorphous substance (the zona pellucida) appears, separating the oocyte from the surrounding follicular cells. Microvilli of the oocyte and filopodia of the follicular cells invade the zonula pellucida and form gap junctions through which they communicate throughout follicular development.

Stromal cells form an inner theca interna, composed mostly of a richly vascularized cellular layer, and an outer theca externa, composed mostly of fibrous connective tissue. The theca interna cells produce the male sex hormone androstenedione, which enters the granulosa cells, where it is converted by the enzyme aromatase into the estrogen estradiol. The granulosa cells are separated from the theca interna by a thickened basal lamina.

Secondary Follicle

Secondary follicles are similar to primary follicles except for the presence of accumulations of liquor folliculi among the granulosa cells.

Continued proliferation of the granulosa cells of the secondary follicle depends on FSH released by basophil cells of the anterior pituitary.

As more fluid is produced, individual droplets of liquor folliculi coalesce to form a single, fluid-filled chamber, the antrum. The granulosa cells become rearranged so that the primary oocyte is now surrounded by a small group of granulosa cells that project out from the wall into the fluid-filled antrum. This structure is called the cumulus oophorus. The loosely arranged low cuboidal granulosa cells immediately adjacent to the zona pellucida move slightly away from the oocyte, but their filopodia remain within the zona pellucida, maintaining contact with the primary oocyte. This single layer of granulosa cells that immediately surrounds the primary oocyte is called the corona radiata.

Most of the follicles that reach this stage of development undergo atresia. A few secondary follicles continue to develop into mature follicles.

Graafian Follicles

Continued proliferation of the granulosa cells and continued formation of liquor folliculi result in the formation of a graafian (mature) follicle whose diameter reaches 2.5 cm by the time of ovulation. The graafian follicle may be observed as a transparent bulge on the surface of the ovary, nearly as large as the ovary itself.

The follicular cells of the wall of the follicle compose the membrana granulosa. Continued formation of liquor folliculi causes the cumulus oophorus composed of the primary oocyte, the corona radiata, and associated follicular cells to become detached from its base to float freely within the liquor folliculi.

By the 14th day of the menstrual cycle, estrogen produced mostly by the developing graafian follicle, but also by secondary follicles, causes elevation of blood estrogen to levels high enough to have the numerous effects, including the shutting off of FSH release and a surge in LH release.

The high blood levels of LH causes the completion of the first phase of meiosis I, resulting in the formation of the secondary oocyte. The secondary oocyte begins, and is arrested in, the metaphase stage of meiosis II. and is released from the graafian follice, a process known as ovulation.

The remnants of the graafian follicle are converted into the corpus hemorrhagicum and then the corpus luteum.

Uterus

The uterus, a single, thick, pear-shaped structure located in the midline of the pelvis, receives at its broad, closed end the terminals of the paired oviducts. It is divided into three regions, the body, fundus, and the cervix.

The uterine wall of the body and the fundus is composed of an endometrium, myometrium, and either an adventitia or a serosa.

The endometrium, or mucosal lining of the uterus, is composed of a simple columnar epithelium and a lamina propria. The epithelium is composed of nonciliated secretory columnar cells and ciliated cells, whereas the lamina propria houses simple branched tubular glands that extend as far as the myometrium The morphological and physiological alterations that occur in the endometrium during the phases of the menstrual cycle are controlled by various hormones.

The endometrium consists of two layers, the functionalis, a thick, superficial layer that is sloughed at menstruation and the basalis, a deep, narrow layer whose glands and connective tissue elements proliferate and thereby regenerate the functionalis during each menstrual cycle.

The functionalis is vascularized by numerous coiled helical arteries that supply the glands and connective tissue. The straight arteries are much shorter and supply only the basalis.

The myometrium is composed of inner longitudinal, middle circular, and outer longitudinal layers of smooth muscle.

Much of the anterior portion of the uterus is covered by adventitia , whereas the fundus and posterior portion of the body are covered by a serosa.

Menstrual Cycle

Menstruation, which begins on the day bleeding from the uterus starts, occurs when fertilization does not take place. The corpus luteum becomes nonfunctional about 14 days after ovulation, thus reducing the levels of progesterone and estrogen. Although the entire functionalis layer of the endometrium is sloughed, it is not completely released from the wall immediately; rather, this process continues for 3 to 4 days.

The proliferative phase (or follicular phase) occurs at the same time as the development of the ovarian follicles. It begins when the menstrual flow ceases, on about day 4, and continues through day 14 by which time the functionalis layer of the endometrium has been fully restored to its previous status with a full complement of epithelium, glands, stroma, and coiled arteries.

The secretory phase (or luteal phase) commences after ovulation. During this phase, the endometrium continues to thicken. The secretory products first accumulate in the basal region of the cytoplasm of the cells constituting the endometrial glands, the granules move apically, and are released into the lumen of the gland. This glycogen-rich material will nourish the conceptus before the formation of the placenta. The secretory phase completes the menstrual cycle as the 28th day approaches, presaging the menstrual phase of a new menstrual cycle.

Observe the correlation with the events occurring in the ovary as well as with the blood hormonal levels.

Mammary Gland

Mammary glands secrete milk, a fluid containing proteins, lipids, and lactose as well as lymphocytes and monocytes, antibodies, minerals, and fat-soluble vitamins.

The glands within the breasts are compound tubuloalveolar glands, consisting of 15 to 20 lobes radiating out from the nipple. Each lobe is drained by its own lactiferous duct where each duct is dilated to form a lactiferous sinus for milk storage and then narrows before reaching the nipple.

Resting or nonsecreting mammary glands of nonpregnant women have the same basic architecture as the lactating (active) mammary gland, except that they are smaller and without developed alveoli, which occur only during pregnancy.

Mammary glands are activated by elevated surges of estrogen and progesterone during pregnancy to become lactating glands to provide milk for the newborn. At this time, the terminal portions of the ducts branch and grow and the alveoli develop and mature

As pregnancy progresses, the breasts enlarge as a result of hypertrophy of the glandular parenchyma and engorgement with colostrum, a protein-rich fluid, in preparation for the newborn. Within a few days after birth, when estrogen and progesterone secretions have subsided, prolactin, secreted by acidophils of the anterior pituitary gland, activates the secretion of milk, which replaces the colostrum.

The secretions of the alveolar cells are of two kinds: lipids and proteins. Lipids are stored as droplets within the cytoplasm. They are released from the secretory cells, possibly by the apocrine mode of exocytosis. Proteins synthesized within these secretory cells are liberated from the cells by the merocrine mode of exocytosis.

Refferences :

• Color Textbook Histology, third edition, leslie P. Gartner
• Basic Histology, tenth edition, L. Carlos Junqueira,2003
• Histology and Cell Biology, second edition,2007
• Elsevier’s Integrated Histology,2007

Read More [...]

Posted in 2012 , genital system , lecture , materi kuliah , reproductive system

Histology of Male Genital System Semester VI (2012)

Contents :

The Male Genital System

The Testis

Spermatogenesis

Genital Ducts

Genital Accessory Glands

The Penis

The Male Genital System

The male reproductive (genital) system consists of the two testes suspended in the scrotum, a system of intratesticular and extratesticular genital ducts, associated glands, and the male copulatory organ, the penis. The testes are responsible for the formation of the male gametes, known as spermatozoa, as well as for the synthesis, storage, and release of the male sex hormone, testosterone.

The glands associated with the male reproductive tract are the paired seminal vesicles, the single prostate gland, and the two bulbourethral glands (of Cowper). These glands form the non-cellular portion of semen (spermatozoa suspended in the secretions of the accessory glands), which not only nourishes the spermatozoa but also provides a fluid vehicle for their delivery into the female reproductive tract.

The penis has a dual function: It delivers semen to the female reproductive tract during copulation and serves as the conduit of urine from the urinary bladder to outside the body.

TESTIS

Each testis is surrounded by a capsule known as the tunica albuginea. Immediately deep to this layer is a highly vascularized loose connective tissue, the tunica vasculosa. The posterior aspect of the tunica albuginea is somewhat thickened, forming the mediastinum testis, from which connective tissue septa radiate to subdivide each testis into approximately 250 compartments known as the lobuli testis

Each lobule has one to four blindly ending seminiferous tubules and small conglomerations of endocrine cells, the interstitial cells (of Leydig) which synthesize testosterone.

Spermatozoa, produced by the seminiferous epithelium of the seminiferous tubules, enter short straight ducts, tubuli recti, that connect the open end of each seminiferous tubule to the rete testis, a system of labyrinthine spaces housed within the mediastinum testis. The spermatozoa leave the rete testis through 10 to 20 short tubules, the ductuli efferentes, which eventually fuse with the epididymis.

The vascular supply of each testis is derived from the testicular artery, which descends with the testis into the scrotum accompanying the ductus deferens (vas deferens).

The capillary beds of the testes are collected into several veins, the pampiniform plexus of veins, which are wrapped around the testicular artery.

Blood in the pampiniform plexus of veins is cooler than that in the testicular artery, reduces the temperature of the arterial blood, thus forming a countercurrent heat exchange system, keeping the temperature of the testes a few degrees lower (35˚ C), than that of the remainder of the body. At this cooler temperature spermatozoa develop normally; at body temperature, spermatozoa that develop are sterile.

THE SEMINIFEROUS TUBULE

The wall of the seminiferous tubule is composed of a slender connective tissue layer, the tunica propria, and a thick seminiferous epithelium, separated from each other by a well-developed basal lamina.

The seminiferous epithelium is several cell layers thick and is composed of two types of cells: Sertoli cells and spermatogenic cells. The latter cells are in various stages of maturation.

The lateral cell membranes of adjacent Sertoli cells form occluding junctions with each other, thus subdividing the lumen of the seminiferous tubule into basal and adluminal compartments. Thus, the zonulae occludentes of these cells establish a blood-testis barrier that isolates the adluminal compartment from connective tissue influences, thereby protecting the developing gametes from the immune system..

Sertoli cells function in: supporting the developing spermatogenic cells; establishing the blood-testis barrier; phagocytosis of cytoplas shed by developing spermatogenic cells; manufacturing the following substances: androgen binding protein (ABP), antimullerian hormone, inhibin, testicular transferrin, and a fructose-rich medium.

SPERMATOGENESIS

Most of the cells composing the thick seminiferous epithelium are spermatogenic cells in various stages of maturation. Some of these cells, spermatogonia, are located in the basal compartment, whereas most of the developing cells—primary spermatocytes, secondary spermatocytes, spermatids, and spermatozoa—occupy the adluminal compartment.

Spermatogonia are diploid cells that undergo mitotic division to form more spermatogonia as well as primary spermatocytes, which migrate from the basal into the adluminal compartment.

Primary spermatocytes enter the first meiotic division to form secondary spermatocytes, which undergo the second meiotic division to form haploid cells known as spermatids.

Spermatids are transformed into spermatozoa by shedding of much of their cytoplasm, rearrangement of their organelles, and formation of flagella.

The maturation process is divided into three phases:

–Spermatocytogenesis: spermatogonia differentiate into primary spermatocytes

–Meiosis: reduction division whereby diploid primary spermatocytes reduce their chromosome complement, forming haploid spermatids

–Spermiogenesis: transformation of spermatids into spermatozoa (sperm)

SPERMATOZOON

Spermatids discard much of their cytoplasm and form a flagellum to become transformed into spermatozoa, a process known as spermiogenesis.

The spermatozoa (sperm) are long cells (~65 μm), composed of a head, housing the nucleus, and a tail, which accounts for most of its length

The tail of the spermatozoon is subdivided into four regions: neck, middle piece, principal piece, and end piece. The plasmalemma of the head is continuous with the tail’s plasma membrane.

The neck (~5 μm long) connects the head to the remainder of the tail. It is composed of the cylindrical arrangement of the nine columns of the connecting piece that encircles the two centrioles, one of which is usually fragmented. The posterior aspects of the columnar densities are continuous with the nine outer dense fibers.

The middle piece (~5 μm long) is located between the neck and the principal piece. It is characterized by the presence of the mitochondrial sheath, which encircles the outer dense fibers and the centralmost axoneme. The middle piece stops at the annulus. Two of the nine outer dense fibers terminate at the annulus; the remaining seven continue into the principal piece.

The principal piece (~45 μm long) is the longest segment of the tail and extends from the annulus to the end piece. The axoneme of the principal piece is continuous with that of the middle piece. Surrounding the axoneme are the seven outer dense fibers that are continuous with those of the middle piece and are surrounded, in turn, by the fibrous sheath.

The end piece (~5 μm long) is composed of the central axoneme surrounded by plasmalemma. The axoneme is disorganized in the last 0.5 to 1.0 μm.

GENITAL DUCTS

Intratesticular Genital Ducts

The intratesticular genital ducts are the tubuli recti (straight tubules), the rete testis, and the ductuli efferentes. These ducts carry spermatozoa and liquid from the seminiferous tubules to the ductus epididymidis.

Most seminiferous tubules are in the form of loops, both ends of which join the rete testis by structures known as tubuli recti. These tubules are recognized by the gradual loss of spermatogenic cells, with an initial segment in which only Sertoli cells remain to form their walls, followed by a main segment consisting of cuboidal epithelium supported by a dense connective tissue sheath.

Tubuli recti empty into the rete testis, contained within the mediastinum, a thickening of the tunica albuginea. The rete testis is a highly anastomotic network of channels lined with cuboidal epithelium.

From the rete testis extend 10-20 ductuli efferentes. They have an epithelium composed of groups of nonciliated cuboidal cells alternating with ciliated cells that beat in the direction of the epididymis. This gives the epithelium a characteristic scalloped appearance. The nonciliated 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 ductuli efferentes gradually fuse to form the ductus epididymidis of the epididymis.

Excretory (extra testicular) Genital Ducts

Excretory genital ducts transport the spermatozoa produced in the testis toward the penile meatus. These ducts are the ductus epididymidis, the ductus (vas) deferens, and the urethra.

The ductus epididymidis is a single highly coiled tube about 4-6 m in length. Together with surrounding connective tissue and blood vessels, this long canal forms the body and tail of the epididymis. It is lined with pseudostratified columnar epithelium composed of rounded basal cells and columnar cells. These cells are supported on a basal lamina surrounded by smooth muscle cells, whose peristaltic contractions help to move the sperm along the duct, and by loose connective tissue rich in blood capillaries. Their surface is covered by long, branched, irregular microvilli called stereocilia. The epithelium of the ductus epididymidis participates in the uptake and digestion of residual bodies that are eliminated during spermatogenesis.

From the epididymis the ductus (vas) deferens, a straight tube with a thick, muscular wall, continues toward the prostatic urethra and empties into it. It is characterized by a narrow lumen and a mucosa with longitudinal folds, covered along most of its extent by pseudostratified columnar epithelium with stereocilia. The lamina propria is rich in elastic fibers, and the 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.

The ductus deferens forms part of the spermatic cord, which includes the testicular artery, the pampiniform plexus, and nerves. Before it enters the prostate, the ductus deferens dilates, forming a region called the ampulla. In this area, the epithelium becomes thicker and extensively folded. At the final portion of the ampulla, the seminal vesicles join 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. The mucous layer of the ductus deferens continues through the ampulla into the ejaculatory duct, but the muscle layer ends after the ampulla.

MALE ACCESORY GENITAL GLANDS

The accessory genital glands produce secretions that are essential for the reproductive function in men. The accessory genital glands are the seminal vesicles, the prostate, and the bulbourethral glands.


The Seminal Vesicles

The seminal vesicles consist of two highly tortuous tubes about 15 cm in length. When the organ is sectioned, the same tube is observed in different orientations. It has a folded mucosa that is lined with cuboidal or pseudostratified columnar epithelium rich in secretory granules. These granules have ultrastructural characteristics similar to those found in protein-synthesizing cells. The lamina propria of the seminal vesicles is rich in elastic fibers and surrounded by a thin layer of smooth muscle. The seminal vesicles are not reservoirs for spermatozoa. They are glands that produce a viscid, yellowish secretion that contains spermatozoa-activating substances such as carbohydrates, citrate, inositol, prostaglandins, and several proteins. The carbohydrates, of which fructose is the most abundant, are the source of energy for sperm motility. Seventy percent of human ejaculate originates in the seminal vesicles. The height of the epithelial cells of the seminal vesicles and the degree of activity of the secretory processes are dependent on testosterone levels.

The Prostate Gland

The prostate gland, the largest of the accessory glands, is pierced by the urethra and the ejaculatory ducts. The slender capsule of the gland is composed of a richly vascularized, dense irregular collagenous connective tissue interspersed with smooth muscle cells. The connective tissue stroma of the gland is derived from the capsule and is, therefore, also enriched by smooth muscle fibers in addition to their normal connective tissue cells.

The prostate gland, a conglomeration of 30 to 50 individual compound tubuloalveolar glands, is arranged in three discrete, concentric layers mucosal, submucosal, and main.

The mucosal glands are closest to the urethra and thus are the shortest of the glands. The submucosal glands are peripheral to the mucosal glands and are consequently larger than the mucosal glands. The largest and most numerous of the glands are the peripheralmost main glands, which compose the bulk of the prostate.

The lumina of the tubuloalveolar glands frequently house round to oval prostatic concretions (corpora amylacea), composed of calcified glycoproteins, whose numbers increase with a person’s age.

The prostatic secretion constitutes a part of semen. It is a serous, white fluid rich in lipids, proteolytic enzymes, acid phosphatase, fibrinolysin, and citric acid. The formation, synthesis, and release of the prostatic secretions are regulated by dihydrotestosterone, the active form of testosterone.

The Bulbourethral Glands

The bulbourethral glands (Cowper's glands), 3-5 mm in diameter, are proximal to the membranous portion of the urethra and empty into it. They are tubuloalveolar 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.

PENIS

The penis is composed of three columns of erectile tissue, each enclosed by its own dense, fibrous connective tissue capsule, the tunica albuginea.

Two of the columns of erectile tissue, the corpora cavernosa, are positioned dorsally; their tunicae albugineae are discontinuous in places, permitting communication between their erectile tissues. The third column of erectile tissue, the corpus spongiosum, is positioned ventrally. Because the corpus spongiosum houses the penile portion of the urethra, it is also called the corpus cavernosum urethrae. The corpus spongiosum ends distally in an enlarged, bulbous portion, the glans penis (head of the penis). The tip of the glans penis is pierced by the end of the urethra as a vertical slit.

The three corpora are surrounded by a common loose connective tissue sheath, but no hypodermis, and are covered by thin skin. Skin continues distal to the glans penis to form a retractable sheath, the prepuce. When an individual is circumcised, it is the prepuce that is removed.

Erectile tissue of the penis contains numerous variably shaped, endothelially lined spaces. The vascular spaces of the corpora cavernosa are larger centrally and smaller peripherally, near the tunica albuginea. However, the vascular spaces of the corpus spongiosum are similar in size throughout its extent.

Refferences :

• Gartner, L.P. and Hiatt, J.L. Concise Histology. 2011

• Color Textbook Histology, third edition, leslie P. Gartner
• Basic Histology, tenth edition, L. Carlos Junqueira,2003
• Histology and Cell Biology, second edition,2007
• Elsevier’s Integrated Histology,2007

Read More [...]

Posted in 2012 , lecture , male genital system , materi kuliah

Struktur Histologi Sistem Saraf- FKG 2012

Materi kuliah blok histologi topik struktur histologis sistem saraf untuk mahasiswa Fakultas Kedokteran Gigi Universitas Mahasaraswati

Download powerpoint : Struktur Histologi Sistem saraf

Read More [...]

Posted in 2012 , fkg , power point , presentation , saraf

Histologi Otot - FKG 2012

Materi kuliah Blok Histologi pada topik otot untuk mahasiswa Fakultas Kedokteran Gigi Universitas Mahasaraswati.

Download Powerpoint : Histologi Otot

Read More [...]

Posted in 2012 , fkg , histologi , otot , power point , presentation