Histology Pre-practical Lecture Slides - Reproductive Systems PDF

# Histology: Human Reproductive System ## HPHS 222 **Dr Meleshni Naicker** Department of Human Physiology University of KwaZulu-Natal [email protected] ## Learning Outcomes - Histology of the Male Reproductive System - Histology of the Female Reproductive System # Histology of the Male Reprodu...

# Histology: Human Reproductive System ## HPHS 222 **Dr Meleshni Naicker** Department of Human Physiology University of KwaZulu-Natal [email protected] ## Learning Outcomes - Histology of the Male Reproductive System - Histology of the Female Reproductive System # Histology of the Male Reproductive System ## Testis - Each testis is an oval structure about 5cm long and 3cm in diameter. - Located in the scrotum. - Covered by: tunica albuginea - a fibrous capsule that covers each testis. - The tunica albuginea gives rise to septa (partitions) that divide the testis into lobules (about 250 lobules). - Each lobule contains 3 or 4 highly coiled seminiferous tubules. - These converge to become rete testis which transport sperm to the epididymis. ### Testis H&E #### Seminiferous tubules - Seminiferous tubules cut in various planes of section. The seminiferous tubules are highly convoluted and are lined by: - **Germ cells** in various stages of spermatogenesis and spermiogenesis, which are collectively referred to as the spermatogenic series. - **Non-germ cells**, called **Sertoli cells**, which support and nourish the developing spermatozoa are also found within the seminiferous tubules. - In the interstitial spaces between the tubules, endocrine cells called **Leydig cells** (which produces male sex hormone testosterone), are found either singly or in groups in the supporting tissue. ## Spermatogenesis - Spermatogenesis is a tightly regulated developmental process that involves sequential mitotic and meiotic cellular divisions, by which developing germ cells differentiate from spermatogonia to spermatocytes, spermatids and finally to spermatozoa. - Spermatogenesis occurs within the seminiferous tubules and is orchestrated by Sertoli cells. - To complete spermatogenesis, differentiating germ cells must migrate through the seminiferous epithelium while maintaining transiently attached to Sertoli cells. ## Interstitial cells of Leydig - Leydig cells are the principal cell type found in the interstitial tissue between the seminiferous tubules. - Produces testosterone in the presence of luteinizing hormone (LH). ### Structure of Leydig cells: - Polyhedral in shape. - Has a large prominent ovoid nucleus, containing 1-3 prominent nucleoli & large amounts of dark-staining peripheral heterochromatin. - Eosinophilic cytoplasm. - Several lipid-filled vesicles. ## Sperm - Sperm is manufactured in the seminiferous tubules within the testicle. ## Rete Testis - The seminiferous tubules converge upon the mediastinum testis, which consists of a plexiform arrangement of channels, the **rete testis** *(RT)*, surrounded by highly vascular collagenous supporting tissue containing myoid cells. - Rete testis is lined by a single layer of low cuboidal epithelial cells with surface microvilli and a single cilium. ## Ductulus Efferens - Rete testis drains into the head of the epididymis via some 15 to 20 convoluted ducts, the **ductuli efferentes** *(DE)*. - The ductuli are lined by a single layer of epithelial cells, some of which are (i) tall columnar and ciliated (ii) and others which are short and non-ciliated. - Ciliary action in the ductuli propels the still non-motile spermatozoa towards the epididymis. - The non-ciliated cells reabsorb some of the fluid produced by the testis. - A thin band of circularly arranged smooth muscle *(SM)* surrounds each ductulus and aids propulsion of the spermatozoa towards the epididymis. ## Epididymis - Receives ductuli efferentes. - Divided into head, body and tail. - **Pseudostratified epithelium** consisting of **principal** and **basal cells**. - **Principal cells** → primary columnar cell of the epididymis and their function is protein secretion & endocytosis. - **Basal cells** → located on the basement membrane throughout the epididymis → regulates the microenvironment where the functionally incompetent sperm cells produced by the testis are matured and stored. - From the proximal to the distal end of the epididymis, the muscular wall increases from a single circular layer smooth muscle, to three layers organised in the same manner as in the ductus deferens. - **Smooth muscle** in head and tail contract spontaneously; smooth muscle in tail requires sympathetic innervation for contraction. - The major function of the epididymis is accumulation, storage and maturation of spermatozoa in the epididymis, the spermatozoa develop motility. ## Vas (ductus) deferens - The vas deferens conducts spermatozoa from the epididymis to the seminal vesicles. - It is a thick-walled muscular tube consisting of inner and outer longitudinal layers and a thick intermediate circular layer. - Like the distal part of the epididymis, the vas deferens is innervated by the sympathetic nervous system, producing strong peristaltic contractions to expel its contents into the urethra during ejaculation. - Similar to that of the epididymis: - The vas deferens is lined by a pseudostratified columnar epithelium. - Smooth muscle arranged in 3 layers. ## Seminal Vesicles - Seminal vesicles secrete 50-70% of the total volume seminal fluid. - The epithelial lining is a pseudostratified tall columnar type and consists of secretory cells with lipid droplets in the cytoplasm, giving it a foamy appearance. - The lumen of each seminal vesicle is highly irregular. - The seminal vesicles produce a yellowish viscid alkaline fluid containing a wide range of substances, including fructose, fibrinogen, vitamin C and prostaglandins. - The prominent muscular wall is arranged into inner circular and outer longitudinal layers and is supplied by the sympathetic nervous system; during ejaculation, muscle contraction forces secretions from the seminal vesicles into the urethra via the ampullae. ## Prostate gland - The secretory product of the prostate, makes about 30-50% the seminal fluid volume. - The prostate gland is composed of glands and stroma. - The supporting stroma *(SS)* is a mixture of collagenous fibrous tissue and smooth muscle fibres. - The glands *(G)* show a convoluted pattern with epithelium thrown up into folds. - The epithelium of the prostate gland contains tall columnar secretory cells with prominent round basal nuclei and pale-staining cytoplasm. - There is also a scanty population of small, flat, basal cells *(B)* at the base of the gland in contact with the basement membrane. ## Penis - The erectile tissues of the penis is arranged into three columns. - Two dorsal columns are called the **corpora cavernosa *(CC)*** and - a single ventral column is called the **corpus spongiosum *(CS)***. - The **penile urethra *(U)*** runs through the center of the corpus spongiosum. - The corpus spongiosum expands at its distal end to form the glans penis. - The erectile corpora (columns) are enclosed within and separated by a **fibrocollagenous capsule *(F)***. ### Primate penis- cross section – H&E – 4x objective - The erectile tissues consist lacunae, spaces that fill with blood, surrounded by collagenous connective tissue (the tunica albuginea). ## Penile Urethra - The penile urethra is lined by stratified or pseudostratified columnar epithelium. - There may also occur some small areas containing stratified squamous epithelium in human adult males. - The external opening called the urethral meatus is lined by stratified squamous epithelium which is continuous with the glans epithelium. - The urethra is lubricated by mucous secretions from the **para-urethral glands *(P)*** and the bulbo - urethral glands of Cowper. # Histology of the Female Reproductive System ## Ovary - Review the basic structure of the ovary and the stages of follicular development. ## Follicle development - Primordial follicles - Undeveloped follicles known as **primordial follicles** are inactive structures, awaiting stimulation from FSH before reentering their developmental pathway. - **Primordial follicles** are composed of a primary oocyte surrounded by a single layer of flattened follicular cells. - The primary oocyte has a large nucleus with dispersed finely granular chromatin, a prominent nucleolus and little cytoplasm. ## Follicle development - Primary follicles - Once stimulated, by FSH, 30-50 primordial follicles re-enter development, and become **primary follicles**. ## Follicle development - Primary follicles - The primary follicle oocyte *(O)* has greatly enlarged and the follicular cells *(F)* have multiplied by mitosis and become cuboidal in shape. - They are now known as **granulosa cells**. - A **zona pellucida *(ZP)*** layer develops between the oocyte and the granular cells – this is a thick homogeneous layer containing glycoprotein and acid proteoglycans. ## Follicle development - Secondary follicle - The **zona granulosa *(ZG)*** continues to proliferate. - In addition, small fluid-filled spaces begin to develop between the granulosa cells, and these fuse to form the **follicular antrum *(FA)***. - This is now referred to as the **secondary follicle**. - At this stage, the **oocyte *(O)*** has nearly reached full size and becomes situated eccentrically within a thickened area of the zona granulosa called the **the follicular antrum**. - The **zona pellucida *(ZP)*** can also be seen in this image. - Stroma around the developing follicle differentiates into **thecal cells**. - At the periphery of the follicle, the **theca folliculi** has developed two layers: - (i) the **theca interna *(TI)***, comprising several layers of rounded cells, - (ii) and the less well-defined **theca externa *(TE)***, consisting of spindle-shaped cells that merge with the surrounding stroma. ## Follicle development - Secondary follicle ## Follicle development - Graafian follicle - On approaching maturity, further growth of the oocyte ceases. This stage in follicular development occurs just before ovulation. - At this stage, the **oocyte *(O)*** is known as the **secondary oocyte**. - The **follicular antrum *(FA)*** is markedly enlarged. - **Zona granulosa *(ZG)*** forms a layer of even thickness around the periphery of the follicle. - At this stage, the maturing follicle has reached between 1.5 and 2.5 cm in diameter and appears as a bulge beneath the ovarian surface. - **Cumulus oophorus** diminishes, and the **oocyte *(O)*** is instead surrounded by the **corona radiata *(CR)*** (i.e a thickened cell layer), which remains attached to the **zona granulosa *(ZG)*** by thin bridges of cells. - At ovulation, the mature follicle ruptures, thus expelling the ovum (comprising secondary oocyte, zona pellucida and corona radiata), into the peritoneal cavity close to the entrance of the Fallopian tube. ## Corpus Luteum - Following ovulation, the ruptured follicle collapses and fills with a blood clot *(B)* to form the **corpus luteum** of menstruation. - The blood clot *(B)* is surrounded by a wide zone of **granulosa lutein cells *(G)***, penetrated by **septa *(S)*** containing large blood vessels. - A thin zone of **theca lutein cells *(T)*** can be seen peripherally. - Externally, the **corpus luteum** is bounded by condensed stromal tissue, that represents the **theca externa** of the Graafian follicle. - The **corpus luteum** serves to provide hormones that are necessary for implantation and early development of a fertilized ovum. ## Corpus Albicans - If fertilization does not occur, the **corpus luteum *(C)*** degenerates & regresses (over approx. 14 days) to become the **corpus albicans** → i.e inactive fibrous tissue mass. - Secretory cells of the degenerated **corpus luteum** undergo autolysis and are therefore phagocytosed by **macrophages *(M)***. ## Female Genital Tract - The female genital tract consists of the: - Fallopian tubes - Uterus - Vagina - All above consists of the same basic structure: - A wall of smooth muscle, - An inner mucosal lining and, - An outer layer of loose supporting tissue. ## Fallopian Tube (Uterine Tube/Oviducts) - The Fallopian tubes serve to carry the released ovum from the ovary to the uterine cavity. - It is also the site of fertilization. - Structurally, the Fallopian tube appears as an elongated funnel that is divided anatomically into four distinct regions as follows: - Fimbria (finger-like projection) - Infundibulum - Ampulla - Isthmus ## Fallopian Tube (Ampulla) - The mucosal lining of the Fallopian tube appears as branching longitudinal folds, a feature that is most prominent in the ampulla, i.e. the usual site of fertilisation. - Micrograph (b) depicts a mucosal fold of the ampulla. These contain a branching core of vascular supporting tissue *(ST)* which comprises a single layer of tall columnar epithelial cells *(E)*. - Micrograph (c) depicts the end of a mucosal fold at high magnification. The columnar epithelial cells are of three types: (i) ciliated, (ii) non-ciliated secretory and (iii) intercalated cells. ## Uterus (Proliferative) - In the **proliferative stage** of the uterine cycle, under control of rising estrogen from the developing follicles, the stratum basalis is regrowing the stratum functionalis, which was shed during the previous menstrual flow. - The diagnostic feature of this stage are the long and straight uterine... ## Uterus (Secretory) - In the **secretory stage** of the uterine cycle, under the control of estrogen and progesterone from the corpus luteum, the uterine glands of the stratum functionalis begin to be functional, producing glycogen. - The diagnostic feature... ## Uterus (Menstrual) - In the **menstrual stage** of the uterine cycle, under the control of lack of estrogen and progesterone from the dead corpus luteum, the stratum functionalis dies and loses its anatomical integrity, ... ## Vagina - The vaginal wall consists of: - A mucosal layer lined by stratified squamous epithelium *(E)*, - A layer of smooth muscle *(SM)* - SM bundles are arranged as inner circular & outer longitudinal layers. - An outer adventitial layer *(A)* - A fibrous lamina propria *(LP)* layer that contains several elastin fibres, has a rich plexus of small veins and is devoid of glands. - The vagina is lubricated by cervical mucus, a fluid transudate from the rich vascular network of the lamina propria, along with mucus secreted by the glands of the labia minora.