FACULTY OF OBSTETRICS AND GYNAECOLOGY NATIONAL POSTGRADUATE MEDICAL COLLEGE OF NIGERIA IN CONJUNCTION WITH FACULTY OF OBSTETRICS AND GYNAECOLOGY WEST AFRICAN COLLEGE OF SURGEONS RIMARY FELLOWSHIP EXAMINATION 16TH – 21ST JUNUARY 2023 STRUCTURE AND FUNCTION OF THE OVARY AND TESTIS ABUBAKAR ABUBAKAR PANTI MBBS , MPH, FWACS, FMCOG, FICS, FMAS. PROFESSOR OF OBSTETRICS & GYNAECOLOGY, UDU/UDUTH SOKOTO INFERTILITY & REPRODUCTIVE ENDOCRINOLOGY UNIT 16th /01/2023 THE OVARY STRUCTURAL ANATOMY The ovary is an almond shaped organ. About 4cm long, 2cm wide and 1cm thick Volume of 5 – 15 cc (mean 10cc) – pre menopausal Develop from the genital ridge It is attached to the back of the broad ligament by the mesovarium Attached to pelvic side wall via the infundibulo -pelvic ligament (suspensory ligament) which contains the ovarian vessels. Attached to the cornu of the uterus via the ovarian ligament OVARIES Each rest on the pelvic side wall in the ovarian fossa Ovarian fossa – is a depression bounded by the External iliac vessels in front The ureter and internal iliac vessels behind It contains the obturator nerve slight depression bw external and internal iliac vessels Vary in dimensions Length – 2.5-5cm Width – 1.5-3cm Thickness – 0.6-1.5cm Ligaments Ovarian (utero-ovarian) ligament connects the ovary to the uterus Infundibular ligament – connects the ovary to the pelvic sidewall Ovarian ligaments = connective tissues and muscles (mesovarium) 4 Ovarian poles Upper pole Broader than the lower pole Related to uterine tube and external iliac vein May be related to appendix on the right Provides attachment to OVARIAN FIMBRIA and INFUNDIBULOPELVIC LIG Lower pole Related to the pelvic floor Provides attachment to ovarian ligament 5 Relations of the ovaries Anterior or mesovarian border Related to the uterine tube & the obliterated umbilical artery Provides attachment to mesovarium & forms the hilus of the ovary Posterior or free border Convex Related to the uterine tube & the ureter Lateral surface Related to ovarian fossa which is lined by parietal peritoneum – separates the ovary from obturator vessels & nerves, ureter and internal iliac art. Medial surface Largely covered by the uterine tube 6 BROAD LIGAMENT • Double layer peritoneum (mesentery) that extends from the side of uterus to the lateral wall and floor of the pelvis • The two layers are continuous with each other at a free edge that surrounds the uterine tube • MESOVARIUM – suspends the ovary • MESOSALPIX – suspends the uterine tube • MESOMETRIUM – below the mesovarium & mesosalpinx • MESOTERES – suspends the round ligament 7 Ovarian artery Ovarian artery is a direct branch of the: aorta on the right left renal artery on the left Enters the broad ligament through the infundibulopelvic ligament. Divides into smaller branches that enter the ovary at the ovarian hilum. As the ovarian artery runs along the hilum, it also sends several branches through the mesosalpinx to supply the fallopian tubes. 8 Ovarian artery Its main stem, however, traverses the entire length of the broad ligament toward the uterine cornu. Here, it forms an anastomosis with the ovarian branch of the uterine artery. This dual uterine blood supply creates a vascular reserve to prevent uterine ischemia if ligation of the uterine or internal iliac artery is performed to control postpartum haemorrhage. Left ovarian vein drains to the renal vein Right ovarian vein drains to the inferior vena cava 9 Blood supply to the ovary and tube 10 The ovary is extremely variable in position The ovary has no peritoneal covering Its surface is covered by fibrous capsule called tunica albuginea which is surrounded on the outside by a thin layer of cuboidal cells - the germinal epithelium An outer ovarian cortex and vascular inner ovarian medulla creates the secondary inner layers (no distinct boundary) Embedded in the cortical and medullary layers is the connective tissue stroma The stroma contains graafian follicles at various stages of development Corpora lutea Corpora albicantia Blood vessels OVARIAN FUNCTION Principally two major functions Gametogenesis Endocrine These (oogenesis) (hormonal) two functions can be intertwined Oogenesis Oogenesis begins early in foetal life. Many degenerate during foetal life, at the time of birth, the number of oocytes is about 1-2 million. All oocytes undergo meiotic arrest when they reach their first meiotic division during foetal life. The primary oocytes remain in the prophase of first meiotic division until the time of puberty when they are gradually released to complete meiosis at regular intervals know as ovarian cycle. Total number of PO at birth = 700,000 to 2M At puberty PO reduces to 400 – 500,000 Follicular activity starts at puberty 15 – 20 follicles recruited monthly ( only one dominates usually from day 6) On the average, only one mature oocyte matures during each ovarian cycle which is approximately on monthly intervals, so that the amount of oocyte to be ovulated is 500 oocytes in a lifetime. Process of Oogenesis Pre-Natal Stage: The primary oocyte grows and gets arrested at meiosis-I They proliferate and form a stratified cuboidal epithelium referred to as granulosa which then secrete glycoproteins around the primary oocyte to form zone pellucida. Antral Stage: The fluid-filled spaces between granulosa cells merge together to form a central fluid-filled space called the antrum. These are referred to as secondary follicles which develop during each monthly cycle under the influence of FSH & LH. Pre-Ovulatory Stage: LH surge induces this stage and meiosis-I is completed here. Inside the follicle are formed two haploid cells of unequal sizes. A polar body forms one of the daughter cells which receives less cytoplasm. This cell is not involved in the development of an ovum. The secondary oocyte is known as the other daughter cell. Meiosis-II occurs in the two daughter cells. The polar body replicates to form two polar bodies whereas the secondary oocyte arrests in the meiosis-II metaphase stage. Process of Oogenesis Ovulation: Within the ovaries, to form a follicle each oocyte surrounded by follicular cells. As the menstrual cycle begins, primary oocytes begin to grow larger, and the number of follicular cells increases, causing the follicle to grow larger too. Some nursing oocytes usually degenerate and leave one follicle only to mature. The primary oocyte begins its primary meiotic division when a follicle reaches maturity and becomes secondary oocyte. Shortly after, in the Fallopian tube, the follicle splits and secondary oocytes are released even though the second meiotic division has not occurred. That release from ovaries of a secondary oocyte is known as ovulation. Fertilization: On fertilization Meiosis-II is complete. This produces a third polar structure. When there is no fertilization, the oocyte degenerates 24 hours after ovulation while remaining arrested in cell division meiosis-II. Oogenesis Structure of a mature ovum • Largest cell in the body. • Consists of cytoplasm and a nucleus with its nucleolus in eccentric position. • Contains 23 chromosomes (23 X ). • Surrounded by a cell membrane called a vitelline membrane. • Outer transparent mucoprotein envelope is called zona pellucida. • Tiny channels in zona pellucida are for the transport of the materials from the granulosa cells to the oocyte. • Space between the vitelline membrane and zona pellucida is called perivitelline space which accommodates the polar bodies. • Oocyte after its escape from the follicle, retains a covering of granulosa cells known as corona radiata derived from the cumulus oophorus. Oogenesis Folliculogenesis Folliculogenesis is the maturation of the ovarian follicle. It describes the progression of a number of small primordial follicles into large preovulatory follicles i.e Graffian follicles that enter the menstrual cycle. OOGENESIS key points There are three stages of folliculogenesis Primary or pre antral follicle (PO) (granulosa cell formation which then surounds the PO) Secondary or antral follicle (vesicular or graafian follicle) xterized by formation of (a) Theca folliculi from granulosa cells (GC) (b) zona pelucida a glycoprotein from GC and oocyte surface cells (c) Differenciation of theca folliculi into theca interna and theca externa (d) Cumulus oophorus from GC surrounding the oocyte Pre ovulatory follicle (37 hours before ovulation) Meiosis II starts but get arrested in metaphase approx 3 hours before ovulation Meiosis II is completed only after fertilization ENDOCRINE FUNCTION The most important endocrine function of the ovary is the production of female sex hormones- mainly estrogen and progesterone (both of which regulates the menstrual cycle amongst other functions) Estrogen production Produced by the granulosa cells of the ovarian follicles and corpora lutea Responsible for the appearance of secondary sex characteristics for females at puberty Maturation and maintenance of the reproductive organs in their matured functional state Theory of initiation of labour (via the ‘oxytocic pathway’) at the end of pregnancy Progesterone production Produced by the corpus luteum Prepares the uterus for pregnancy Prepares the mammary gland for lactation Others Testosterone (50% of testosterone in females is produced by the ovary and the adrenal gland) Anti Mullarian hormone (AMH)- produced by the granulosa cells – measures ovarian reserve Inhibin Relaxin (the ovary release relaxin before delivery to loosen the pelvic ligaments) THE TESTIS STRUCTURAL ANATOMY Ball like structure housed by the scrotum Left testis lies at a lower level than the right within the scrotum Each testis is covered by fibrous capsule called the tunica albuginea (TA) The TA invaginates anteriorly into a double serous covering- the tunica vaginilis Along the posterior-lateral border of the testis lies the epididymis The epididymis structured into expanded head, a body and pointed tail inferiorly Medially there is a grove (sinus epididymis) between the epididymis and the testis The epididymis is covered by the tunica vaginalis except at its posterior margin Both the testis and the epididymis bear at their upper end a small nodular body called the Appendix testis and Appendix epididymis respectively (Hydatid Morgagni) The testis consist of 200-300 lobules each containing 1-3 seminiferous tubules Each seminiferous tubule is about 62cm long, coiled and convoluted The tubules forms anastomosis posteriorly into a plexus called the rete testis About a dozen fine efferent ducts arises from the rete testis The ducts pierce the tunica albuginea at the upper part of the head of the epididymis The head of the epididymis is actually formed by the coiling of the efferent ducts The efferent ducts fuse thereafter to form a considerably convoluted single tube The The body and the tail of the epididymis tail of the epididymis empties into the vas deference(ductus deferens) BLOOD SUPPLY Testicular artery: branch from the aorta at the level of the renal vessel Testicular vein: forms from the pampiniform plexus of veins Right drains inferior vena cava Left to the renal vein DEVELOPMENTALLY Testis develop from genital ridge (mesodermal) Migrate caudally to its position 3rd month= reaches the Iliac fossa 7th month= transverse the inguinal canal 8th month= reaches the external ring 9th month= descends into the Scrotum APPLIED ANATOMY Hernia Hydrocoele Vaginal: confined to the scrotum Congenital: communicates with the peritoneal cavity Infantile: extends up to the internal ring Hydrocoele of the cord: confined to the cord TESTICULAR FUNCTION Two major functions Gametogenesis Endocrine (hormonal) Both (spermatogenesis) functions could be intertwined Testes has two fxnal components Seminiferous tubule (comprising (90 - 95%) and Interstitium (formed from intertubular tissues) – has Lydig cells that produces testosterone SPERMATOGENESIS A complex biological process of cellular transformation that produces male haploid germ cells from diploid spermatogonial stem cells SPERMATOGENESIS cont Seminiferous tubules are lined by layers of germ cells at various stages of devpt (spermatogonia, spermatocytes, spermatide, sperm) and Supporting cells SERTOLI CELLS which provides nutritional and mechanical support to spermatogenic cells The process of spermatogenesis is initiated at puberty Principally 3 phases Spermatogonial phase (mitosis) Spermatocyte phase (meiosis) Spermatid phase (spermiogenesis) SPERMATOGENESIS cont There are about 3 million spermatogonia that begins the process each day Each spermatogonium give rise to 16 primary spermatocytes via mitotic division Each of the spermatocytes enters meiosis and give rise to 4 spermatids (hapliod) The spermatids then undergoes maturation process to spermatozoa which are released into the lumen of seminiferous tubule = SPERMIOGENESIS Formation of acrosome Condensation of nucleus Formation of neck, middle piece & tail Cytoplasmic shedding SPERMATOGENESIS cont SPERMATOGENESIS cont Daily about 200M potential spermatozoa produced (3x16x4) Half of these die during the process of development thus 100M are eventually produced per day Average of 64 – 70 days for production About 14 days for transportation through the epididymis to ejaculatory duct Sperm matures along the transport line SPERMATOGENESIS cont Follicle stimulating hormone (FSH) and testosterone are the hormones controlling spermatogenesis FSH receptors are on Sertoli cells and spermatogonia Testosterone production in Leydig cells is under the control of Luteinizing hormone (LH) Testosterone binds to sertoli cells to promote spermatogenesis Intratesticular testosterone is about 100x greater than that in peripheral circulation FSH acts directly on sertoli cells in spermatogenesis process while LH acts through Leydig cells- testosterone Role of sertoli cells in spermatogenesis Support and nutrition of developing germ cells Compartmentalization of the seminiferous tubule by tight jxn – provide protective environment for developing germ cells Controlled release of matured spermatids into tubular lumen Secretion of fluid, protein and several growth factors Phagocytosis of the degenerating germ cells Spermatogenesis SUMMARY OF SPERMATOGENESIS There are about 3 million spermatogonia that begins the process each day Each spermatogonium give rise to 16 primary spermatocytes via mitotic division Each of the spermatocytes enters meiosis and give rise to 4 spermatids (haploid) The spermatids then undergoes maturation process to spermatozoa which are released into the lumen of seminiferous tubule = SPERMIOGENESIS Formation of acrosome Condensation of nucleus Formation of neck, middle piece & tail Cytoplasmic shedding Spermatogenesis Haploid gametes (n 23) n Egg cell n Sperm cell Meiosis Ovary Fertilization Testis Diploid zygote (2n 46) 2n Key Multicellular diploid adults (2n 46) Mitosis Haploid stage (n) 47 Diploid stage (2n) Oogenesis Spermatogenesis: Oogenesis: 1. It occurs in the testes. 1. It occurs in the ovaries. 2. Spermatogonia change to primary spermatocytes. 2. Oogonia change to primary oocytes. 3. A primary spermatocyte divides to form two secondary spermatocytes. 3. A primary oocyte divides to form one secondary oocyte and one polar body. 4. A secondary spermatocyte divides to form four spermatids. 4. A secondary oocyte divides to form one ootid and one polar body. 5. No polar body is formed. 5. Polar bodies are formed. 6. A spermatogonium forms four spermatozoa. 6. An oogonium forms one ovum. 7. Sperms are minute yolkless and motile. 7. Ova are much larger often with yolk and nonmotile. 8. It is generally completed in the testes and thus mature sperms are released from the testes. 8. It is often completed in the female reproductive tract or in many animals in water because oocytes are released from the ovaries. Endocrine function Androgen synthesis Precursor is cholesterol Major androgen is testosterone Site of production is Leydig cells ( discovered in 1850 by Franz Leydig –German anatomist) Role of testosterone Differentiation , development and maturation of external and internal reproductive organs Stimulation Regulation of spermatogenesis of accessory sex gland function Development of secondary sex characteristics Regulation of gonadotropin secretion by negative feed back mechanism mood and cognitive function Vascular effect (negative effect) Antimullarian (AMH) and Inhibin B synthesis by sertoli cells Secretion of Androgen binding protein (ABG) and Plasminogen activator by sertoli cells Oestrogen synthesis Aromatization 15% of testosterone of total daily 50mcg of oestrogen is produced by the testis CONCLUSION The ovary and the testis originates from the same sourcegenital ridge Structurally dissimilar Functionally similar (gametogenesis and endocrine) with some variation in timing of their functions However the ovary ages earlier than the testis THANK YOU FOR LISTENING SUCCESS TO YOU ALL References Chaudhry SR, Chaudhry K. StatPearls [Internet]. StatPearls Publishing; Treasure Island (FL): Aug 23, 2020. Anatomy, Abdomen and Pelvis, Uterus Round Ligament. Roly ZY, Backhouse B, Cutting A, Tan TY, Sinclair AH, Ayers KL, Major AT, Smith CA. The cell biology and molecular genetics of Müllerian duct development. Wiley Interdiscip Rev Dev Biol. 2018 May;7(3):e310. Sajjad Y. Development of the genital ducts and external genitalia in the early human embryo. J Obstet Gynaecol Res. 2010 Oct;36(5):929-37. Thomas DFM. The embryology of persistent cloaca and urogenital sinus malformations. Asian J Androl. 2020 MarApr;22(2):124-128. de Ziegler D, Pirtea P, Galliano D, Cicinelli E, Meldrum D. Optimal uterine anatomy and physiology necessary for normal implantation and placentation. Fertil Steril. 2016 Apr;105(4):844-54 Chaurasia BD. Female reproductive organs. In: Human Anatomy Regional and Applied 2nd ed. New Delhi: CBS; 1991. p311 – 324.
