Anatomy Book PDF: Genital System

GAD-102 The female reproductive system (or female genital system)  Internal: The female internal reproductive organs are the vagina, uterus, uterine tubes (Fallopian tubes, oviducts) and ovaries.  External: external genitalia (skin...

GAD-102 The female reproductive system (or female genital system)  Internal: The female internal reproductive organs are the vagina, uterus, uterine tubes (Fallopian tubes, oviducts) and ovaries.  External: external genitalia (skin folds) 1 Ovaries  a pair of small glands about the size and shape of almonds,  Located on the left and right sides of the pelvic body cavity.  Ovaries produce female sex hormones such as estrogen and progesterone as well as ova (commonly called "eggs"). Page 52 Faculty Of Medicine – Sohag University GAD-102 2 Fallopian Tubes  A pair of muscular tubes that extend from the left and right superior corners of the uterus to the edge of the ovaries.  The fallopian tubes end in a funnel-shaped structure called the infundibulum, which is covered with small finger-like projections called fimbriae.  The fimbriae swipe over the outside of the ovaries to pick up released ova and carry them into the infundibulum for transport to the uterus.  The inside of each fallopian tube is covered in cilia that work with the smooth muscle of the tube to carry the ovum to the uterus. 3 Uterus (womb) a hollow, muscular, pear-shaped organ The lower part known as the cervix Connected to the two fallopian tubes on its superior end and to the vagina (via the cervix) on its inferior end, The inner lining of the uterus, known as the endometrium, provides support to the embryo during early development When fertilization does not occurs endometrium breakdown in the form of menstruation at the end of the cycle. The visceral muscles of the uterus contract during childbirth to push the fetus through the birth canal. 4 Vagina  An elastic, muscular tube that connects the cervix of the uterus to the exterior of the body.  Its outer opening lies posterior to the urethra and closed in virgins by a thin membrane (hymen). Page 53 Faculty Of Medicine – Sohag University GAD-102 Male Reproductive (genital) System 1) Scrotum  A sac-like organ made of skin and muscles that houses the testes.  The scrotum is made up of 2 side-by-side pouches with a testis located in each pouch.  Testis )plural testis)  2) The 2 testes are the male gonads responsible for the production of sperm and testosterone.  The testes are ellipsoid glandular organs around 1.5 to 2 inches long and an inch in diameter.  Each testis is found inside its own pouch on one side of the scrotum. NOTE NB: The scrotum is located outside of the body to keep the temperature of the testis below the average body temperature, which is an essential factor for sperm production.  Epididymis )within scrotum)  3) d  The epididymis is a sperm storage area that wraps around the superior and posterior edge of the testes.  The epididymis is thin tubules that are tightly coiled into a small mass.  Sperm produced in the testes moves into the epididymis to mature before being passed on through the male reproductive organs.  Consists of head (above), body and tail below. The ductus deferens  4) Page 54 Faculty Of Medicine – Sohag University GAD-102  Known as the vas deferens  30-45 cm  A muscular tube that carries sperm superiorly from the epididymis tail into the abdominal cavity to the ejaculatory duct. 5) Ejaculatory duct )2cm)   The union of the ductus deferens with the ducts from the seminal gland (seminal vesicle).  During ejaculation, the ejaculatory duct opens and expels sperm and the secretions from the seminal vesicles into the urethra.  The urethra in males is a common pathway for urine and semen. Page 55 Faculty Of Medicine – Sohag University GAD-102 How many chromosomes do people have? o In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46. o Twenty-two of these pairs, called autosomes, look the same in both males and females. o The 23rd pair, the sex chromosomes, differ between males and females. Females have two copies of the X chromosome, while males have one X and one Y chromosome. o The 22 autosomes are numbered by size. The other two chromosomes, X and Y, are the sex chromosomes. This picture of the human chromosomes lined up in pairs is called a karyotype. Definition of some Terms A karyotype: is an individual's collection of chromosomes. o o The term also refers to a laboratory technique that produces an image of an individual's chromosomes. o The karyotype is used to look for abnormal numbers or structures of chromosomes. Chromosomes: o thread-like structures located inside the nucleus of animal and plant cells. o The term chromosome comes from the Greek words for color (chroma) and body (soma). Scientists gave this name to chromosomes because they are cell structures, or bodies, that are strongly stained by some colorful dyes used in research. o Each chromosome is made of protein and a single molecule of deoxyribonucleic acid (DNA). o Passed from parents to offspring, DNA contains the specific instructions that make each type of living creature unique. Page 57 Faculty Of Medicine – Sohag University GAD-102 o Chromosomes are divided into two chromatids with a constriction point called a centromere in the middle. Mitosis: o Mitosis is a process where a single cell divides into two identical daughter cells (cell division). o During mitosis one cell divides once to form two identical cells. o The major purpose of mitosis is for growth and to replace worn out cells. Miosis: o Meiosis is a process where a single cell divides twice to produce four cells containing half the original amount of genetic information. These cells are our sex cells – sperm in males, eggs in females. o During meiosis one cell Divides twice to form four daughter cells. o These four daughter cells only have half the number of chromosomes? of the parent cell – they are haploid. o Meiosis produces our sex cells or gametes (eggs in females and sperm in males). o Meiosis occurs through 2 stages (meiosis I) followed by (meiosis II):In meiosis I, homologous chromosomes separate, while in meiosis II, sister chromatids separate. Page 58 Faculty Of Medicine – Sohag University GAD-102 Primary Sex organs Structure of the testis  1)  The testis consists of about 250 compartments each of which lodges 2-3 highly convoluted tubules called seminiferous tubules.  Each seminiferous tubule has a blind end and a straight open end which joins a network of tubules called the rete testis.  This rete testis communicates with the epididymis by efferent ductules called vasa efferentia.  In Brief: Testis >>> 250 compartments >>> 2-3 seminiferous tubules >>> Rete testis >>> Vasa efferentia >>> epididymis Scrotum  1) Page 59 Faculty Of Medicine – Sohag University GAD-102 The seminiferous tubule  The wall of the seminiferous tubule consists of several layers of germ cells. The cells lying on the basement membrane are the most primitive and called spermatogonia (form sperms).  Scattered among the germ cells are special type of supporting cells called Sertoli cells (supporting cells) which assist in maturation of the sperms.  In between the seminiferous tubule scattered cells called the leydig cells which secrete hormones (testosterone). Transverse section through seminiferous tubule Magnified part of the semineferous tubule Page 60 Faculty Of Medicine – Sohag University GAD-102 2) Structure of the ovary  The ovary consists of an outer cortex and an inner medulla. The cortex lodges the ovarian follicles which undergo maturation after puberty to produce ova(ovum). Gametogenesis  The process by which mature gametes (sperms or ova) are formed from primitive sex cells (genesis = formation).  In the male, gametogenesis is called spermatogenesis and results in the formation of sperms, while in the female, it is called oogenesis and results in the formation of mature ova  Spermatogenesis is a continuous process extending from puberty to old age, while oogenesis extends only from puberty to menopause (menopause is stoppage of menstruation which occurs at the age of 45-50 years). Page 61 Faculty Of Medicine – Sohag University GAD-102 1) Spermatogenesis  The process, by which fully formed sperms (spermatozoa) are produced from primitive sex cells called Spermatogonia. Steps of spermatogenesis: 1. Spermatogonia:  Spermatogonia (singular: spermatogonium) are the most primitive sex cells which lie directly on the basement membrane of the seminiferous tubule.  Each spermatogonium divides by mitosis (no reduction of chromosomes) into 2 daughter cells called “type A” and “typeB” Spermatogonia )each has 46 chromosomes). NOTE The “type A” cell remains in contact with the basement membrane (for further mitotic division), while “type B”cell continues maturation to form a primary spermatocyte. 2. Spermatocytes: 2) The “type B” spermatogonium enlarges in size and becomes transformed into a primary spermatocyte (still having 46chromosomes=diploid). 3) The primary spermatocyte undergoes the 1st meiotic division(with reduction of the chromosomes to their half number=haploid). 4) This result in 2 daughter cells called secondary spermatocytes each of which contains 23 chromosomes. 5) The secondary spermatocyte is carrying either Y-chromosome (form male) or X- chromosome (form female). 3. Spermatids: Each secondary spermatocyte undergoes the 2nd meiotic divisionto form2 daughter cells called spermatids each of which still has 23 chromosomes. 4. Spermiogenesis: This is the process by which the spermatids are transformed from rounded cells to complete sperms by the support of Sertoli cells. This transformation Page 62 Faculty Of Medicine – Sohag University GAD-102 involves a number of morphological changes in the cytoplasm of the spermatid as follows:  Formation of head cap: the Golgi apparatus is transformed into the head or acrosomal cap which covers the anterior ½ of the head of the sperm. This cap is active enzymatically and thus facilitates penetration of the sperm into the ovum.  Formation of axial filament: derived from one of the centrioles which elongates and forms the middle piece as well as tail of the sperm.  Formation of mitochondrial sheath: derived from the mitochondria which condense and form sheath around the middle piece.  Formation of the head of the sperm: it is actually the nucleus of the spermatid. NOTE It takes about 3 months for the spermatogonium to form 4.complete mature sperms Structure of the mature sperm: It consists of head, neck, middle piece and tail.  Head: consists of the nucleus together with the acrosomal cap covering its anterior half.  Neck: is the narrow junction between the head and the middle piece.  Middle piece: consists of the axial filament together with the surrounding mitochondrial sheath.  Tail: is the terminal part of the axial filament.  The length of the whole sperm is about 60 microns Page 63 Faculty Of Medicine – Sohag University GAD-102 Seminal fluid: composed of 2 components: sperms and secretions. 1. Sperms: In the normal ejaculate(3-5 cc) the sperms are present in a concentration of 100 million sperms per cc. 2. Secretions are produced by the accessory sex glands; these are: seminal vesicles, prostate and bulbo-urethral glands. Sperm transport: The sperms leave the seminiferous tubules and pass through the following ducts: rete testis > vasa efferentia > epididymis > duct deferens > ejaculatory duct and finally the urethra from which they are ejaculated. The movement of the sperms is by 3 main mechanisms: a) Ciliary movement of the lining cells of the rete testis and vasa efferentia. b) Peristaltic contraction of the muscle wall of the duct deferens. c) Active forward projecting motility of the sperms  The accessory sex glands pour their secretions over the sperms to form the seminal fluid. These glands are:  seminal vesicles  prostate  bulbo-urethral glands. Page 64 Faculty Of Medicine – Sohag University GAD-102 Page 65 Faculty Of Medicine – Sohag University GAD-102 2) Oogenesis  the process by which mature ova (singular ovum) are produced from primitive sex cells called oogonia (singular oogonium).  It is a cyclic process, i.e. it occurs once every month. (This contrasts with spermatogenesis which is a continuous process.) The Intra-uterine stage: -oogonia: Early during intra-uterine life, the ovary contains only oogonia which reach about 5,000,000 by the 5th month. Then, the majority of the oogonia degenerate while the surviving ones become transformed into much larger cells called primary oocytes. -primary oocytes: These primary oocytes remain arrested in the prophase stage of meiotic division I from the intrauterine life until sexual maturity. -primordial follicle: Each primary oocyte is surrounded by a layer of flat follicular cell to form the primordial follicle. The primordial follicles remain dormant until puberty when they start maturation NOTE -The total number of primary oocytes diminishes from about 1,000,000 at birth to about 40,000 at puberty. -Oogenesis takes place in the cortex of the ovary, where only one ovarian follicle completes maturation every month under the effect of the follicle stimulating hormone (F.S.H) secreted by the anterior lobe of pituitary gland. Steps of oogenesis (Occurs every month after puberty) Page 66 Faculty Of Medicine – Sohag University GAD-102 I. Maturation of primordial follicle: The primordial follicle consists of main components: a primary oocyte and follicular cells surrounding the oocyte. 1. Maturation of the primary oocyte: -The primary oocyte (contains 46 chromosomes) undergoes the 1st meiotic division giving rise secondary oocyte (23 chromosomes) and a small mass of nuclear material called 1st polar body (23 chromosomes) which is situated at the pole of the cell (hence its name polar) and contains no cytoplasm. -The secondary oocyte, then, starts the 2nd meiotic division; this division is not completed only at the time of fertilization when the ovum is penetrated by the sperm. 2. Maturation of the follicular cells:  formation of the primary follicle: -The follicular cells of the primordial follicle divide repeatedly by mitosis to form several layers around the oocyte. These cells accumulate granules in their cytoplasm, and thus are called granulosa cells - The granulosa cells become separated from the oocyte by a thick hyaline membrane called zona pellucida (pellucid = transparent).  Formation of the secondary follicle: -Small cavities filled with fluid appear between the granulosa cells. These cavities then form a single cavity called follicular antrum. -The follicular antrum separates the granulosa cells into 2 layers (outer and inner): 2. Outer layer: forms called stratum granulosum (stratum = layer) 3. Inner layer: surrounds the secondary oocyte and bulges into the antrum as an elevation called cumulus oophores (cumulus = elevation; oophores= bearing the ovum). Page 67 Faculty Of Medicine – Sohag University GAD-102  Formation of mature (Graafian) follicle Pressure increases inside the antrum To the outside of the stratum granulosum, a sheath of stroma cells (cells of the ovary itself) is formed around the whole follicle and called the theca follicle (theca = sheath). The theca is divided into 2 layers (external and internal): 1-Theca externa: outer layer and consists of fibrous tissue and big blood vessels 2-Theca interna: inner layer and consists of cells and fine blood vessels (These cells are the main source of estrogen hormone). II)Rupture of graafian follicle (OVULATION): -Once the Graafian follicle becomes fully mature, it comes to lie close to the surface of the ovary. -It then ruptures through overlying cortex of the ovary which is thin and ischemic at the site of rupture. -Ovulation takes place 14 days before the beginning of the following menstrual cycle. -As a result of rupture, the secondary oocyte together with surrounding zona pellucida and corona radiata is discharged from the ovary to enter the uterine tube Page 68 Faculty Of Medicine – Sohag University GAD-102 The following factors leading to the rupture of the follicle 1. Increase in size of the follicle. 2. Thinning of the overlying cortex of the ovary. 3. Rise of the pressure of the fluid inside the follicular antrum Ovulated oocyte NOTE -The fimbriae of the uterine tube covering this ovary guide the ovulated oocyte to enter the uterine tube - The corona radiata is formed by the granulosa cells which remain.attached to the zona pellucida and stay around it after ovulation III. Formation of corpus luteum -Following ovulation, the wall of the Graafian follicle collapses and rapidly undergoes luteinization (appearance of yellow pigment in the wall of the follicle). -This luteinization takes place under effect of the luteinizing hormone (L.H.) secreted by the pituitary gland. -As a result, the Graafian follicle becomes transformed into a yellow body called corpus luteum (corpus = body; luteus = yellow). -These luteinized cells secrete progesterone hormone, but few of the theca interna cells continue to secrete estrogen hormonethe progesterone hormone increases in the blood while the estrogen hormone decreases. Page 69 Faculty Of Medicine – Sohag University GAD-102 IV. Fate of corpus luteum: It degenerates after some time and transforms into a white fibrous mass called corpus albicans (albus = white). There are 2 types of corpuses luteum: 1. In absence of fertilization: the corpus luteum degenerates within 10 days of ovulation and is called corpus luteum of menstruation. 2. In case of fertilization: the corpus luteum remains active for a longer period (4-5 months) until the placenta becomes fully functioning and then the corpus luteum degenerates. It is called corpus luteum of pregnancy. Page 70 Faculty Of Medicine – Sohag University GAD-102 OVARIAN CYCLE (28 days) OVARIAN CYCLE (28 days) A series of changes which take place in the ovary every month, under the effect of the follicle stimulating hormone (F.S.H.) and the luteinizing hormone (L.H.). These hormones are secreted by the pituitary gland. PHASES:  Follicular phase (Begin from the 1st day of menstrual flow)  Starts by secretion of F.S.H. which initiates maturation of the primordial follicle to become the mature Graafian follicle  During maturation, the estrogen hormone is secreted by the cainterna cells of the Graafian follicle. 2) Ovulation (at day 14): The Graafian follicle ruptures and the ovum (in the stage of secondary oocyte) is extruded to enter the uterine tube. The wall of the Graafian follicle is then transformed into the corpus luteum. 3) Luteal phase: (stage of formation of corpus luteum under effect of the luteinizing hormone (L.H.) secreted by the pituitary gland) The progesterone hormone increases in the blood while the estrogen hormone decreases. The estrogen and progesterone hormones act in the following ways a) They suppress secretion of F.S.H. of the pituitary gland, this preventing maturation of further primordial follicles during the same cycle. b) They pass to the endometrium of the uterus (through the blood) which responds by proliferation as well as by increasing activity of its glands. At the end of the ovarian cycle, the corpus luteum degenerates (corpus luteum of menstruation) and becomes the corpus albicans leading to cessation of secretion of the estrogen and progesterone hormones. As a result, the F.S.H. released again from the pituitary gland and a new ovarian cycle starts in the ovary. If fertilization takes place, the corpus luteum continues functioning for a longer period (corpus luteum of pregnancy), and the ovarian cycles will stop until after childbirth, when they start again. Page 71 Faculty Of Medicine – Sohag University GAD-102 MENSTRUAL MENSTRUAL CYCLE CYCLE A series of changes which occur in the endometrium of the uterus every month under the effect of the ovarian hormones (estrogen and progesterone). It lasts 28 days, i.e. one lunar month, and its beginning is marked by the passage of menstrual blood flow. Phases (stages): The menstrual cycle is divided into 3phases: A) Phase of menstrual flow: In this phase, the menstrual blood flows for about 3-5 days. This blood (about 50 cc) consists of the following: 1. Shedded epithelium of the endometrium. However, the basal layer of the endometrium is left intact for further regeneration. 2. Secretions of the degenerated uterine glands. 3. Venous and arterial blood: from the degenerated vessels. B) Proliferative phase (also called follicular phase): It lasts for about 10 days. It is under the influence of estrogen hormone (only) and ends by the time of ovulation. The basal part of the endometrium (left after shedding) shows proliferation of its 3 main constituents: glands, vessels and stroma cells, as follows: 1. Glands: grow in size, increase in number and become tubularin shape 2. Blood vessels: grow in size and increase in number (but not yet spiral). 3. Stroma cells: divide and thus increase in number (but not in size). This phase is also called estrogenic phase because it is under the influence of estrogens secreted by the Graafian follicle. C) Secretory phase (pregestational or luteal phase): 6) It follows the proliferative phase, i.e. just after ovulation. It I under the influence of the progesterone hormone secreted by the corpus luteum It lasts for about 10 days after the time of ovulation. 7) The endometrium as a whole becomes thicker, edematous and its epithelium becomes tall columnar and undergo the following changes: 1. Uterine glands: become dilated and distended with secretion and rich in glycogen and mucin. 2. Blood vessels: become dilated and spiral and show many arterio-venous anastomoses. 3. Stroma cells: become large in size due to accumulation of glycogen and lipids. Page 72 Faculty Of Medicine – Sohag University GAD-102 NOTE This phase ends by cessation of secretion of progesterone and estrogen (because of degeneration of the corpus luteum) which results in degeneration of the surface epithelium and shedding of the endometrium, thus marking the beginning of the menstrual flow of the next cycle.. Page 73 Faculty Of Medicine – Sohag University