Female Reproductive System Histology PDF

XY2141. HISTOLOGY. FEMALE REPRODUCTIVE SYSTEM PART II Dr Viktoriia Yerokhina, Lecturer in Medical Sciences [email protected] 1  LEARNING OUTCOMES HIST.23.10 -...

XY2141. HISTOLOGY. FEMALE REPRODUCTIVE SYSTEM PART II Dr Viktoriia Yerokhina, Lecturer in Medical Sciences [email protected] 1  LEARNING OUTCOMES HIST.23.10 - Distinguish between the perimetrium, myometrium and endometrium HIST.23.11 - Describe the arrangement of blood vessels and glands in the functional and basal layers HIST.23.12 - List the principal features of the proliferative, secretory and menstrual phases HIST.23.13 - Explain what triggers the onset of the menstrual phase HIST.23.14 - Compare the endocervix and the exocervix HIST.23.15 - Describe the wall of the vagina and give the source of vaginal secretions 2  UTERUS A nonpaired hollow muscular organ of pear-like shape, whose mucous membranes undergo cyclic changes to create the most suitable environment for implantation and the development of an embryo, and later the fetus taking place in this area. PARTS: Body Fundus Isthmus Cervix 3 Metra and hystera are Greek terms for uterus.  UTERUS Canal of cervix opens into the uterine cavity through internal os, whereas into the vagina through external os. 4  WALL OF THE UTERUS Wall of the uterus is formed of 3 layers: I. Mucosa (endometrium), II. Muscularis (myometruim), III. Serosa (perimetrium). Both myometrium and endometrium undergo cyclic changes each month to prepare the uterus for implantation of an embryo. These changes constitute the menstrual cycle. If an embryo implants, the cycle stops, and both layers undergo considerable growth and differentiation during pregnancy. 5  MUCOSA - ENDOMETRIUM Mucosal lining of uterus is called endometrium. Endometrium consists of: 1) simple columnar epithelium, 2) lamina propria – stroma – fibrous layer of the mucosa, contains simple tubular glands (uterine glands); 6  MUCOSA - ENDOMETRIUM 1) Simple columnar epithelium, that contains: a) ciliated cells – less numerous columnar ciliated cells b) secretory cells – majority of the epithelial cells; has columnar shape and release a secretion with high amount of glycoproteins and glycogen; c) basal cells - stem cell for the renewal of mucosa Epithelium Epithelium Lamina propria - stroma Lamina propria - stroma 7  MUCOSA - ENDOMETRIUM 2) Lamina propria – stroma - fibrous layer of the mucosa with blood and lymph vessels and nerve fibers formed mainly by reticular fibers, amorphous extracellular mucopolysaccharides and two main cell types: a) Stromal endometrial cells – fibroblast-like cells, which undergo l changes due to the effect of hormones preparing for eventual implantation of the embryo by storing glycogen and lipids in the cytoplasm (predecidual change) in case of the fertilization of the ovum, they change to decidual cells containing a storage of substances intended for the initial nourishment of the embryo (decidual change) b) Endometrial granular cell / Hamplerl cells – T-lymphocyte of spherical shape and markedly lobular nucleus present mainly in the secretory phase of the menstrual cycle releasing cytokines, which affect the growth of the embryonic trophoblast at its implantation and control the growth and multiplication of vessels in the mucosa contains simple tubular glands (uterine glands). 8  UTERINE GLANS (GLANDULAE UTERINAE) Uterine glands (glandulae uterinae) – simple tubular (unbranched or slightly branched) glands lined with simple columnar epithelium with predominant secretory cells Passing through the whole mucosa layer, their shape and activity vary in the individual phases of the menstrual cycle. 9  BLOOD SUPPLY OF THE UTERUS Uterus is supplied by a pair of uterine arteries. Each uterine artery gives arcuate branches that give radial arteries, which supply the myometrium. In the myometrium, radial arteries divide into two types of arteries: straight arteries are in stratum basale, spiral arteries which are long and coiled in the stratum functionale. During menstruation, spiral arteries are shed along with the stratum functionale. 10  Zones of the endometrium On the basis of the cyclical changes endometrium is divided into 2 zones: 1. Basal layer - deeper layer; is not sloughed off during menstruation but functions as a regenerative zone after its rejection; is supplied by straight arteries. 2. Functional layer - superficial layer, which constitutes about 80% o the endometrial thickness; it is sloughed off during every menstruation; site of cyclic changes in the endometrium; is supplied by spiral arteries. 11  Zones of the endometrium Schematic diagram showing two layers of uterine endometrium, stratum functionale and stratum basale, and its blood supply in proliferative and 12 secretory phases. Zones of the endometrium 13  MYOMETRIUM Composed of 3 layers of smooth muscle tissue. Middle layer is the thickest layer; contains numerous large blood vessels and is called stratum vascularis. It has smooth muscle bundles oriented in a circular or spiral pattern. Inner and outer layers contain smooth muscle bundles oriented parallel to the long axis of the uterus. 14  MYOMETRIUM Smooth muscle cells – located in a network of collagen and elastic fibers in a non-pregnant woman, they are 50 µm long; during pregnancy, their size increases (hypertrophy) up to 500 µm and simultaneously, their number increases, too (hyperplasia) Interconnected by numerous gap junctions, which multiply during pregnancy and facilitate the synchronicity of the cells during the contractions. 15  MYOMETRIUM Blood vessels are present in between the smooth muscle bundles. The rhythmic contraction of these muscles may intensify during menstruation and cause cramps. At parturition, the hormone oxytocin induces powerful contractions of the uterine muscles to expel the fetus. 16  PERI- AND PARAMETRIUM Perimetrium - outer serous layer or visceral peritoneal covering of the uterus, is continuous with the pelvic and abdominal peritoneum Perimetrium has two layers: Outer layer of mesothelium (simple squamous epithelium) Inner layer of vascular connective tissue Parametrium - fibrous layer covering the subperitoneally located part of the uterus. 17  MENSTRUAL (UTERINE) CYCLE Menstrual (uterine) cycle is a continuum of developmental stages in the functional layer of the endometrium, normally repeating every 28 days. Menstrual cycle has 3 successive phases: I. Menstrual II. Proliferative III. Secretory 18  MENSTRUAL PHASE (1- 4-5 DAYS) At the end of the secretory phase ovarian hormone levels rapidly decrease; Spiral artery are sensitive to a lack of hormones → walls of the spiral arteries contract → close off the blood flow → ischemia → death (necrosis) of their walls and of the functional layer of the endometrium. At this time, blood vessels above the constrictions rupture, and bleeding begins. The average blood loss in the menstrual phase is 35 to 50 mL. Only the basal layer containing basal parts of uterine glands are left. Proliferation of the gland cells in the basal part and migration of the cells to the surface initiate the proliferative phase. 19  PROLIFERATIVE PHASE (5-14 DAYS) Initiated under the influence of estrogens, that are present in the growing follicules in the ovary at the same moment. The lost epithelium is regenerated from the basal portions of the uterine glands. At the end of the proliferative phase the endometrium is 2-3 mm thick, glands are straight tubules with narrow lumens. 20  SECRETORY PHASE (15-28 DAYS) Secretory phase is regulated by progesterone of the corpus luteum. Glands become highly coiled and secrete glycoproteins that will be the major source of embryonic nutrition before implantation occurs. Endometrium reaches its maximum thickness (5 mm) as a result of the accumulation of secretions and the edema of the stroma. The last few days of this period is called ischemic phase. The sequential influence of estrogens and progesterone on the stromal cells enables their transformation into decidual cells. The stimulus for transformation is the implantation of the blastocyst. 21  SECRETORY PHASE (15-28 DAYS) Secretory stage is the stage when blastocyst can be implanted into the uterine endometrium. 22 MENSTRUAL (UTERINE) CYCLE 23  UTERINE GLANDS Simple tubular glands (#4 in the pic.) → lined by columnar epithelium Mucous fluid produced by the glands is rich in glycogen, required to support placental 24 development if implantation occurs.  UTERINE GLANDS At the time of menstruation the greater parts of the uterine glands are lost (along with the entire lining epithelium) leaving behind only their most basal parts. In the proliferative phase the uterine glands are straight. As the endometrium increases in thickness the glands elongate, increase in diameter, and become twisted on themselves. In secretory phase the glands enlarge and become corkscrew-shaped, and their lumina become sacculated as they fill with secretory 25 products. SUMMARY 26  ENDOMETRIOSIS Endometriosis is a common gynecologic disease in which endometrial tissue appears at unusual locations in the lower abdomen and pelvis. It affects females between puberty and menopause but is most common between the ages of 20 and 30 years. Symptoms include pelvic pain and premenstrual bleeding. Of unknown etiology, the disorder may result when endometrial cells peel off the uterine lining during the menstrual cycle and migrate via fallopian tubes to the peritoneal cavity. The condition often subsides after menopause, when estrogen stimulation declines. 27  UTERINE CERVIX Part of the uterus below the isthmus. Endometrium of the cervix differs from the rest of the uterus. A part of the cervix protrudes through the vagina; it is called the vaginal part of the cervix. The vaginal part of the cervix is surrounded by a circular furrow, the vaginal fornix. The cervix encloses a narrow cervical canal, which communicates with the uterine cavity through the internal os and with the vagina through the external os. 28  FEATURES OF THE UTERINE CERVIX Mucosa = epithelium + lamina propria. Underneath the mucosa, there is the CT+ some smooth muscles which form the bulk of the cervix. Cervical canal is lined by simple columnar epithelium. Lamina propria consists of CT with numerous cervical glands. At the external os, the epithelium changes to non-keratinised stratified squamous epithelium. It continues over the vaginal part of the cervix and further with the epithelium of the vagina. Cervical mucosa is not shed during menstruation. 29  FEATURES OF THE UTERINE CERVIX The site where the epithelium changes from simple columnar to non-keratinised stratified squamous is known as transformation zone (squamocolumnar junction). Transformation zone is the most common site of origin of carcinoma cervix. 30  PAP (PAPANICOLAOU) SMEAR Cervical epithelial cells are constantly shed off (exfoliated) into the vagina. These cells can be collected, stained, and observed for routine screening and diagnosis of cancerous conditions of the cervix. This smear of cells on the glass side is called a pap smear. Surface scraping is done by a cervical spatula/brush/broom, around the external os. The cells in the scraping are studied under the microscope. 31 [Georgios Papanikolaou, Greek cytopathologist, 1883–1962]. CERVICAL CYTOLOGY PAPANICOLOU (HP) Surface cells of the stratified squamous epithelium have small, contracted nuclei and are stained pink due to the cytoplasmic keratin. Deeper cells have plump nuclei of normal appearance, and the cytoplasm is stained blue/green. An adequate Pap smear should also contain some endocervical cells (demonstrating that the transformation zone has been sampled), as well as cervical mucin and inflammatory cells. 32  CERVICAL GLANDS mucus-secreting branched tubular glands Secretory activity of the glands undergoes cyclical changes during the menstrual cycle. During the proliferative phase of the menstrual cycle their secretions are watery (to allow easier passage of the sperm), During the secretory phase the secretions become highly viscous (to prevent the passage of the microorganism from the vagina into the cervix). 33  CERVICAL GLANDS Blockage of the openings of the mucosal glands results in the retention of their secretions, leading to formation of Nabothian cysts. Nabothian cysts develop frequently but are clinically important only if numerous cysts produce marked enlargement of the cervix. 34  VAGINA Fibromuscular tube extending from the vaginal part of the cervix to the external genitalia. THE WALL: 1. Mucosa, 2. Muscularis, 3. Adventitia. Mucosa Epithelium is non-keratinised stratified squamous epithelium. Lamina propria - dense CT. Vaginal mucosa is devoid of glands, and it is lubricated by mucus secreted by cervical glands. Muscularis Inner circular and outer longitudinal layers of smooth muscle. Adventitia 35 Contains many elastic fibers → elasticity of the wall of the vagina. VAGINA 36  VAGINA Cells of the vaginal epithelium contain abundant amounts of glycogen and consequently often have a pale-staining appearance with conventional stains such as hematoxylin and eosin. When these cells are shed into the vaginal lumen, the glycogen is converted to lactate by bacteria, resulting in an acid pH that helps depress the growth of foreign microorganisms. 37 Mucosa of the vagina  VESTIBULAR GLANDS There are two types of vestibular glands, both are structures found near the vaginal opening: Greater, or major, vestibular glands are also known as Bartholin's glands; Lesser, or minor vestibular glands also known as Skene's glands. 38  BARTHOLIN'S GLANDS – GREAT VESTIBULAR GLANDS Two pea sized compound racemose glands located slightly posterior and to the left and right of the opening of the vagina. Bartholin's glands secrete mucus to provide vaginal lubrication. 39  EXTERNAL GENITALIA Female external genitalia, or vulva, include several structures, all covered by stratified squamous epithelium: Vestibule, a space whose wall includes the tubulo-acinar vestibular glands; Paired labia minora, folds of skin lacking hair follicles but with numerous sebaceous glands; Paired labia majora, homologous and histologically similar to the skin of the scrotum; Clitoris, an erectile structure homologous to the penis with paired corpora cavernosa. 40 Stay healthy! 41 References