Kharkov National Medical University Department of Histology Female Reproductive System Part I (ovaries, uterus)

Internal female reproductive organs: the ovaries, oviducts, uterus vagina.

OVARY The ovaries have two functions: production of oocytes secretion of hormones.

Ovary = Cortex + Medulla

Ovary - structure Surface: Simple cuboidal (“Germinal”) epithelium and tunica albuginea – con. tiss.

Cortex = follicles Ovarian follicles consist of one oocyte and surrounding follicular cells.

Note: Follicular development can be divided into a number of stages.

Primordial Follicles Smallest (25μm) are located in the cortex just beneath tunica albuginea.

Primordial Follicles = Consist of : One layer of flattened follicular cells surround the oocyte

Primordial Follicles Nucleus

Primary follicles: follicular cells become cuboidal, first – unilaminar, one layer of F.C. (125μm)

Multilaminar Primary follicles: Proliferation of granulosa cells result in the formation of a stratified epithelium surrounding the oocyte - multilaminar. The zona pellucida ( ) becomes visible. Connective tissue cells of the ovary surrounding the growing follicle become organised in concentric sheaths, the theca folliculi.

thecal cells (vascularized) granulosal cells Primary follicle: multilaminar (no liquor folliculi)

Secondary follicle has antrum, which is the defining feature of the secondary follicle. theca folliculi differentiates with the continued growth of the follicle into a theca interna (start to produce oestrogens) and theca externa.

Ovarian Follicles

Graafian follicle Is the mature or tertiary or preovulatory follicle

Ovulation

Ovulation The Graafian follicle forms a small "bump" on the surface of the ovary, the stigma (or macula pellucida). The stigma is characterised by a thinning of the capsule and a progressive restriction of the blood flow to it. The follicle finally ruptures at the stigma and the oocyte is released from the ovary. Only about 400 oocytes ovulate during life.

The Corpus Luteum - Yellow Body - temporary endocrine structure The C.L. is formed by both granulosa cells and thecal cells after ovulation has occurred.

The Corpus Luteum The wall of the follicle collapses into a folded structure, Vascularization increases and a connective tissue network is formed.

The Corpus luteum - Yellow body Theca interna cells and granulosa cells start accumulating lutein within a few hours after ovulation. They are now called granulosa lutein cells and theca lutein cells and produce progesterone and oestrogens.

The Corpus luteum - Yellow body Hormone secretion in the corpus luteum ceases within 14 days after ovulation if the oocyte is not fertilised. In this case, the corpus luteum degenerates into a corpus albicans - whitish scar tissue within the ovaries. Hormone secretion continues for 2-3 month after ovulation if fertilisation occurs.

Corpus albicans

About 99.9 % of the oocytes that where present at the time of puberty undergo atresia. Atresia is the name for the degenerative process by which oocytes and follicles degenerate without having been expelled by ovulation. atresia affects follicles at various stages of their development . Atresia

Ovarian Cycle

The Oviduct The oviduct functions as a conduit for the oocyte from the ovaries to the uterus.

The Oviduct consists of t. mucosa and a t.muscularis. The peritoneal surface of the oviduct is lined by a t. serosa and subjacent connective tissue.

T. mucosa is formed by a ciliated and secretory epithelium resting on a lamina propria. ciliated cells beat in both directions

T. muscularis consists of an inner circular muscle layer and an outer longitudinal layer.

The Uterus The uterus is divided into body (upper two-thirds) and cervix.

The Uterus The walls of the uterus are composed of a mucosal layer, the endometrium, and a fibromuscular layer, the myometrium. The peritoneal surface of the uterus is covered by a serosa - perimetrium.

Myometrium Smooth muscle tissue form 3-4 layers. The muscular tissue hypertrophies during pregnancy. Oxytocin

Endometrium consists of simple columnar epithelium (ciliated cells and secretory cells) and an underlying thick connective tissue stroma.

The endometrium Many simple tubular uterine glands extend through the entire thickness of the stroma.

zona basalis and zona functionalis. The endometrium is subject to cyclic changes that result in menstruation and can be divided into two zones based on their involvement in the changes during the menstrual cycle: zona basalis and zona functionalis.

Zona functionalis is the luminal part of the endometrium. It is sloughed off during every menstruation and it is the site of cyclic changes in the endometrium.

Zona basalis is not sloughed off during menstruation but functions as a regenerative zone for the functionalis after its rejection.

Uterine artery Arcuate artery Radial artery The Uterus Endometrium Straight artery Spiral artery Gland - Stratum Functionalis - Stratum basalis

The cyclic changes of endometrium are called the menstrual cycle. There are three phases of the menstrual cycle: Menstrual - desquamation phase. Postmenstrual or proliferative phase (or follicular), Premenstrual or secretory phase (or luteal), Only the mucosa of the body of the uterus takes part in the menstrual cycle.

Postmenstrual or Proliferative phase - In the postmenstrual phase the endometrium is thin represented by basal layer. Under the influence of estrogens produced by the growing follicle endometrium is reconstituted.

This phase lasts from the end of menstruation till about 14-th days

Premenstrual or secretory phase At day when ovulation occurs in the ovary and yellow body begins its development and next, premenstrual or secretory phase begins. This phase is under the control of progesterone.

The uterine glands enlarge and become produce the mucous secret.

The spiral arteries become more coiled The spiral arteries become more coiled. The stromal cells transformate into decidual cells. These are large pale cells rich in glycogen. The corpus luteum remains active for only about 10 days if fertilization does not occur.

Menstrual phase The menstrual or desquamation phase results from a decline in the ovarian secretion of progesterone and estrogen due to the involution of the corpus luteum.

Menstrual phase The sharp decline of the hormone levels results to the contraction of the spiral arteries, lasting for several hours.

Menstrual phase This spasm causes ischemia (blood deficiency) in the stratum functionale. During this brief period the blood vessels are ruptured.

Menstrual phase Subsequent relaxation of the spiral arteries results to the blood flow into the stratum basale. As a result the stratum functionale undergoes to the desquamation.

Menstrual phase The period of menstrual flow normally lasts for about 5 days. In the absence of fertilization a cessation of bleeding would accompany the growth and maturation of new ovarian follicle. So next cycle begins.

Menstrual phase