Reproductive System - Notes PDF

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Reproductive System Function – production, storage, nourishment, and transport of functional male and female reproductive cells (gametes) Anatomy of male reproductive system – External organs – Penis – tubular organ through which the distal portion of the urethra passes It contains modified sebaceous glands that produce a waxy secretion (smegma) Glans – expanded head that surrounds the external urethral orifice Prepuce – foreskin that surrounds the tip of the penis Erectile tissue –composed of maze of vascular channels surrounded by elastic connective tissue and smooth muscle This tissue fills with blood during sexual arousal Corpus cavernosa – Corpus spongiosum –

Scrotum – fleshy pouch suspended from the perineum at the base of the penis that keeps testes at a cooler temperature for sperm development The internal layer is a serous membrane that reduces friction between the scrotal and testicular surfaces Ejaculatory In gans – form a continuous tube duct primary reproductive organ of male system Flattened egg shape organs that sit within the scrotum Each testis is covered by a dense layer of connective tissue that subdivides the interior into lobules each containing roughly 800 coiled seminiferous Bulbourethral tubules gland Glans

Spermatogensis – formation & maturation of sperm Seminiferous tubules – tightly coiled tubules distributed throughout testes where sperm are produced Interstitial cells – scattered between seminiferous tubules, these cells produce male sex hormones Nurse cells (aka sustentacular cells) – located inside the tubules, these cells maintain a bloodtestis barrier, support of spermatogenesis, et al. Hormone secretion – testes secrete testosterone which is tightly controlled by a negative feedback loop Development & maintenance of secondary sexual characteristics Stimulates protein synthesis Promotes growth of skeletal muscles, bones, & skin Local effects of sperm development in seminiferous tubules Behavioral changes Epididymus – tightly coiled tubule at the posterior border of each testis that is the site of sperm storage, recycling for damaged spermatozoa, and facilitation of maturation of sperm Van deferens (aka ductus deferens) – long muscular tube (~18 in) that leads from the epididymus into pelvic cavity through inguinal canal to posterior side of the bladder where they unite together at the prostate gland Peristaltic contractions can move substances along the duct Ejaculatory Duct – junction of the van deferens at the seminal vesicle that opens into the prostatic urethra about halfway through the prostrate gland Urethra – passageway from bladder to outside

Accessory organs – responsible for secreting fluid component of semen Seminal vesicles (aka seminal glands) – paired glands that lie dorsal to bladder that secrete viscous liquid rich in fructose, prostaglandins, fibrinogen & other nutrients that make up ~60% of semen Slightly alkaline to neutralize acids of vagina and prostate gland Prostate gland – small gland directly below bladder that secretes a thin, slightly acidic fluid with seminalplasmin that protects sperm in the vagina Bulbourethral gland (aka Cowper gland) – paired, pea-shaped glands below prostate at the urogenital diaphragm that produce a clear mucus solution during arousal that lubricates the tip of the penis & neutralizes acidity in urethra to protect sperm Semen – fluid that contains sperm & glandular secretions Physiology of male reproductive tracts – Anterior pituitary – serves as primary control of reproductive function by secreting FSH & LH in response to gonadotropin-releasing hormone from the hypothalamus GnRH is released at a steady rate after puberty FSH targets nurse cells & LH induces testosterone production Spermatogenesis – occurs in the testes Spermatogonia (sperm stem cells) – dormant in childhood but spermatogonia begin to divide through mitosis at puberty Located along the outer wall of the seminiferous tubules Primary spermatocytes – enlarged spermatogonia that are ready to undergo mitosis Meiosis I – primary spermatocytes undergo meiosis producing secondary spermatocytes that are unique Secondary spermatocytes contain half the number of chromosomes as spermatogonia

Meiosis II – secondary spermatocytes undergo meiosis II to produce haploid spermatids

Structure of sperm – Head – Neck – Tail –

Anatomy of female reproductive system – External sexual organs – function in sensory arousal & lubrication Vulva – external opening of vagina Mons pubis – Labia majora – large flaps of adipose skin with hair that covers the vaginal entrance It marks outer limits of vulva Labia minora – small flaps of hairless skin immediately surrounding vestibule Clitoris – Bartholins gland – located along the posterolateral margins of vaginal entrance, these glands secrete mucus to lubricate vulva

Breasts (mammary glands) – produce nutrient rich milk for nursing infants Anatomy – each gland lies within pectoral fat pad & is composed of lobes of secretory cells that produce milk

Lactiferous ducts –

Nipple – small conical projection where the ducts open onto the body It is surrounded by reddish brown skin called the areola that contains large sebaceous glands

Internal structures – Ovaries – pair of small almond shaped organs near side walls of pelvic cavity Function – Oogenesis – formation of eggs Hormone secretion – mainly progesterone & estrogen Estrogen – development/maturation of reproductive tract, secondary sex characteristics & behavioral changes Progesterone –primes tissues causing endometrial thickening & further development of mammary glands Inhibin – important in the feedback loop for control of FSH Anatomy – Germinal epithelium – thin layer of columnar epithelium that covers each ovary Tunica albuginea – fibrous connective tissue deep to the germinal epithelium that protects the ovaries Follicles – specialized structures where oocytes grow & begin develop Mesentery supports –

Ovarian ligament – connects ovary to uterus preventing sup nferior movements of the organs Broad ligament – extensive mesentery that supports & encloses most of female reproductive tract by attaching to the sides and wall of the pelvic cavity where it becomes continuous with parietal peritoneum Suspensory ligament (aka infundibulopelvic ligament) – connects ovary to pelvic wall that limits the superior/inferior movements of the organs and provides a route of entry for ovarian blood vessels

Fallopian tubes (aka uterine tube or oviduct) – hollow muscular tubes ~5 in. long that sit next to the ovary to receive the egg and conduct it to uterus Infundibulum – expanded end of tube that surrounds ovary with feathery projections that drape over the ovary without touching it The inner surfaces are lined with cilia for movement of egg into and along the tube Fertilization will occur in the tube within 12 to 24 hours of ovulation Uterus – muscular pear-shaped organ that receives egg from fallopian tubes & provides place for fetal development Regions of uterus – 1. Fundus – rounded portion of the uterus that is superior to the attachment of the uterine tubes 2. Body – 3. Cervix – tubular portion that extends into vagina

Uterine wall anatomy – Perimetrium – outer layer of visceral peritoneum composed of serous tissue Myometrium – thick muscular middle layer composed of a longitudinal, circular, and oblique layers that provide the force needed to move the fetus out of the uterus & into the vagina Represents ~90% of the mass of the uterus Endometrium – inner mucus membrane with lots of uterine glands that secrete mucus and nutrients for the growing embryo This layer changes under the influence of estrogen and is incompletely shed each month during menstruation Uterine support – uterus supported by 8 ligaments from peritoneum Round ligaments – paired ligaments that connects uterus to the connective tissues of the external genitalia Vagina – elastic, muscular tube ~3 in. long that leads from the uterus to the outside of body It functions as a passageway for menses and the baby during partuition & receives penis during sexual intercourse The vaginal canal is lined with muscosa to secrete lubricating fluids and underlying smooth muscles Epithelium is thrown into folds or rugae Hymen – fold of mucosa that covers entrance to vagina that is ruptured during first intercourse, tampon insertion & through strenuous activity Physiology – Anterior pituitary – serves as primary control of reproductive function by secreting FSH & LH The pituitary responds to gonadotropin-releasing hormone from hypothalamus that varies in pulse frequency and amplitude over the course of the 28 day uterine and ovarian cycles

In general, GnRH causes release of FSH which in turn slowly stimulates release of LH Oogenesis – monthly production of eggs Oogonia (immature egg stem cells) – multiply by mitosis during gestation Primary oocytes – each daughter cell develops within primordial follicles from oogonia during reproductive years through meiosis I The oocytes is halted here until puberty As FSH levels rise & the ovarian cycle begins, several primordial follicles develop into primary follicles monthly & begin to produce estrogen Zona pellucida – area of attachment between the follicular cells and oocyte (primary oocyte) It is composed of microvilli from both follicular cells and oocyte and does not dye well so it appears translucent Secondary follicles – follicle wall thickens and cells begin to secrete follicular fluid (antrum) Fluid surrounds primary oocyte on both sides Tertiary follicle – primary oocyte surrounded by antrum that is surrounded by a mass of granulosa cells Secondary oocyte – after the tertiary follicle is finished development, rising LH levels prompts finishing of meiosis I yielding a secondary oocyte within the follicle and a small polar body Corona radiata – secondary oocyte loses contact with the follicle wall and moves towards the center of the follicle where it is still surrounded by follicular cells called the corona radiate This corona will be released with the secondary oocyte and must be penetrated by the sperm

Ovarian cycle –

Follicular phase (~14 days) – single follicle matures & secondary oocyte is released at ovulation when the follicular wall ruptures Oocyte is moved to the fallopian tube by the fimbriae and cilia of the fallopian tube Ovulation – LH surges & GnRH pulse frequency increases Luteal phase (~ 14 days) – the gransulosa cells of the empty tertiary follicle develops into corpus luteum Corpus luteum is an endocrine structe that secretes progesterone to prepare the uterus for implantation At ~12 days after ovulation, the progesterone and estrogen levels in the environment will drop radically if the egg is not fertilized, resulting in disintegration of the corpus luteum Menstrual cycle (aka uterine cycle) – repeating series of changes in the endometrium that averages 28 days in length Menses – shedding of endometrial lining begins uterine cycle (~7 days) that occurs after blood flow to the area is reduced significantly, tissue degrades and weakened arterial walls rupture The site begins to repair as soon as the lining is shed Proliferative phase – endometrial cells proliferate as developing follicle begins to secrete estrogen in response to FSH (~7 days) By the end of this phase, the uterine glands are secreting glycogen rich mucus essential for the survival of the fertilized egg Results in a thick endometrium Secretory phase – uterine glands enlarge and secrete mucus and nutrients while arteries that supply the endometrium elongate under the combined effects of estrogen and progesterone

Aging & Disorders – Aging – fertility & sexual function decline with age due to declining levels of hormone Climacteric – changes in physiology of reproductive tract in both men and women beginning around age 50 Women – go through climacteric and menopause at the same time – ovarian function declines, less estrogen & progesterone secreted, vagina becomes thinner, bone mass declines, & hormone balances shift quickly Men – sperm count & libido decrease with decreasing levels of testosterone...