Reproductive System Notebook PDF

Notebook – Reproductive System 2024-08-29 2:28 PM Male Reproductive System: Functions Gonads Produce gametes – sperm Produce hormones...

Notebook – Reproductive System 2024-08-29 2:28 PM Male Reproductive System: Functions Gonads Produce gametes – sperm Produce hormones Male reproductive structures include the external genitalia and internal genitalia External Genitalia: Penis Contains erectile tissue, deposits sperm into vagina Urethra Conducts semen to exterior Scrotum Surrounds and supports testes Internal Genitalia: Testes Produce sperm and hormones Epididymis The site of sperm maturation Ductus deferens (Vas Deferens) Conduct sperm between epididymis and prostate Seminal gland (seminal vesicles) Secretes fluid making up much volume of semen Prostate Secretes fluid and enzymes Bulbo-urethral glands Secretes fluids that lubricate tip of penis Path of Sperm 1. Made in the testes 2. Moved to the epididymis 3. Then along the ductus deferens 4. Then along the ejaculatory duct to the urethra Accessory organs Secrete various fluids into the reproductive tract along the way Seminal glands Prostate Bulbourethral glands Secrete various fluids into ejaculatory duct and urethra Scrotum & Associated Structures: Scrotum Cutaneous outpouching of the abdomen that houses and supports the testes Scrotal septum Separates right and left cavities Marked by a raised thickening (raphe of scrotum) in the scrotal surface Dartos Muscle Smooth muscle in the skin of the scrotum Elevates testes (not as much as the cremaster) and contracts the scrotum (reduces heat loss) Causes the scrotum to get wrinkly Cremaster Muscle Contracts to pull testes closer to body during sexual arousal or when exposed to cold temperature Spermatic Cords Extend through the inguinal canals between testes and abdominopelvic cavity Each contains layers of fascia and muscle enclosing: Ductus deferens Blood vessels (testicular artery and veins) Nerves Lymphatic vessels The Testes – Testicles: Form inside the body cavity adjacent to the kidneys Late in fetal development (~7 months) connective tissue band contracts Pulls each testis through abdominal musculature into the scrotum Cryptochidism – testes do not descent (risk factor for testiclular cancer) Tunica vaginalis Outer layer: Serous membrane derived from peritoneum partially covers testes Just like other serous membranes, fluid can collect here Called a hydrocele Tunica albuginea Inner layer: Dense, white, irregular CT capsule, deep to tunica vaginalis Extends inward to form many septa, which form 200-300 lobules Each lobule filled with 2 or 3 seminiferous tubules This is where spermatogenesis happens Cells of the Seminiferous Tubules: Spaces between tubules contain... 1. Areolar tissue 2. Blood vessels 3. Large interstitial endocrine cells (Leydig Cells) Produce androgens, such as testosterone and androstenedione (dominant sex hormones in males) 4. Sustentacular cells (Sertoli cells or Nurse cells) Extend from basement membrane to lumen of seminiferous tubule Protect, support, nourish developing sperm phagocytize excess spermatid cytoplasm Produce fluid for sperm transport Release sperm into lumen Release inhibin (hormone) Form blood-testis barrier Isolate developing gametes from blood Prevents immune response from developing against spermatogenic cells surface antigens b/c they are "foreign" The walls of the Seminiferous tubules Also contains the developing sperm cell at different stages of development Spermatogonia – stem cells Spermatocytes – undergoing meiosis Spermatids – undergoing spermiogenesis (develop into mature sperm) Spermiation Process in which a sperm loses attachment to the nurse cell and enters the tubule lumen Spermatogenesis: The development of sperm Complete maturation takes 65 – 75 days Millions of sperm produced per day 4 basic steps include: 1. Creation of many spermatogonium through mitosis 2. Meiosis to create gametes 3. Spermiogenesis to create functional sperm 4. Spermiation Steps: 1. Creation of many spermatogonium through mitosis Spermatogonium Diploid cells Stem cells that undergo mitosis Some stay near basement membrane of seminiferous tubule for future cell divisions and sperm production Some squeeze through tight junctions to other side of blood-testes border and differentiate into primary spermatocytes Starts at puberty 2. Meiosis Primary spermatocytes Diploid Undergo meiosis I Result in 2 secondary spermatocytes Secondary spermatocytes Haploid Undergo meiosis II Results in 4 spermatids (all connected) Different 3. Spermiogenesis Spermatids undergo spermiogenesis No cell division, spermatid changes into sperm Cell changes shape from spherical to elongated Forms acrosome (cap) & flagellum (tail) Mitochondria multiply Sustentacular cells dispose of excess cytoplasm Takes 24 days for spermatids to mature 4. Spermiation Spermiation is when sperm cells are released from sustentacular cell connections into the lumen of seminiferous tubules Sperm are not yet able to swim, so fluid in tubule pushes them toward ducts of testes Structure of Sperm: Specialized to deliver chromosomes to female gamete Lack most organelles and intracellular structures in order to reduce size and mass Head Nucleus with 23 chromosomes Spermatozoa/spermatozoom = sperm Acrosome Cap filled with proteins (hyaluronidase & proteases - break down protein) to penetrate ovum Tail (flagellum) Whiplike organelle that moves the sperm Capacitation Spermatogonia stem cells – through mitosis Sperm released from testes are physically mature But immobile and incapable of fertilizing an oocyte Spermatocytes undergoing meiosis Other parts of male reproductive system are responsible for functional maturation, Spermatids undergoing spermiogenesis (develop into mature sperm) nourishment, storage, and transport of spermatozoa Capacitation is the process enabling sperm to become motile and fully functional – ability to fertilize an egg Spermiation sperm cells are released from sustentacular cell connections into the lumen of seminiferous tubules Usually occurs in 2 steps: Sperm are not yet able to swim, so fluid in tubule pushes them toward ducts of testes 1. Sperm become motile when mixed with seminal gland secretions Spermatogenesis The development of sperm 2. Sperm become capable of fertilization when exposed to the female reproductive tract Spermiogenesis Spermatids undergo spermiogenesis - MATURATION No cell division, spermatid changes into sperm Epididymis: Cell changes shape from spherical to elongated Forms acrosome (cap) & flagellum (tail) Start of the male reproductive tract Takes 24 days to mature Coiled tube bound to posterior border of each testis Capacitation the process enabling sperm to become motile and fully functional – ability to fertilize an egg Lined with pseudostratisfied columnar epithelium Usually occurs in 2 steps: Has long stereocillia that increase surface area Branching microvilli that increase SA for reabsorption of degenerated sperm that were stored & not ejaculated 1. Sperm become motile when mixed with seminal gland secretions 2. Sperm become capable of fertilization when exposed to the female reproductive tract Sperm undergo functional maturation here and storage (up to a month) Spermatozoa/spermatozoom Aka sperm Regions of the Epididymis: Won't ask these Head Receives spermatozoa from efferent ductules Body Extends inferiorly along the posterior surface of the testis Tail Starts near the inferior border of the testis Number of coils decreases Connects with the ductus deferens Histology: Lined with pseudostratified ciliated columnar epithelium Layer of smooth muscle Propels sperm onward w/ peristaltic contractions during sexual arousal Ductus Deferens (vas deferens): Stores sperm and propels them toward the urethra during ejaculation Can store sperm for several months before they degenerate Pathway 1. Ascends along posterior border of epididymis 2. Passes up through spermatic cord and inguinal ligament 3. Reaches posterior surface of urinary bladder 4. Joins ducts of seminal vesicles to form ejaculatory duct 5. Empties into prostatic urethra Histology Lined with pseudostratified columnar epithelium Covered with heavy coating of muscle Convey sperm through peristaltic contractions Ejaculatory ducts: Union of seminal vesicle ducts & ducti deferens Eject spermatozoa into the prostatic urethra Urethra: Shared terminal duct of the reproductive and urinary systems Passageway for semen and urine 3 portions: 1. Prostatic 2. Membranous 3. Spongy (cavernous) Seminal Glands (seminal vesicles): Sandwiched between the posterior wall of the urinary bladder and the rectum Secretion ejected by smooth muscle lining gland Alkaline: neutralizes vaginal & male urethral acid Fructose: sperm ATP production Prostaglandins: motility and viability Stimulates flagellum movement in sperm First step of capacitation Produce ~60% of semen volume Prostate Gland: Encircles the proximal urethra as it leaves the bladder Roughly the size of a golf ball Produces 20 – 30 % of semen volume Secretions contain: 1. Seminalplasmin Antibiotics that may help prevent urinary tract infections in males 1. Proteolytic enzymes to liquefy semen Prostate-specific antigen (PSA), pepsinogen, lysozyme, amylase, and hyaluronidase Prostate-specific antigen (PSA) Produces naturally in the body Liquefies semen Hyper produced = pathological problems 3. Citric acid Sperm ATP production Bulbo-urethral Glands (Cowper's glands): Located at the base of the penis Duct of each gland empties into the urethra Secrete thick, alkaline mucus Helps neutralize acids in the urethra Also lubricates the tip of the penis Semen: Semen contains sperm and seminal fluid Seminal fluid is from accessory glands Slightly alkaline, milky appearance 2.5 to 5 ml released per ejaculation Normal sperm count is 50 to 150 million/ml - the smallest cell a human can make Once ejaculated, semen coagulates w/in 5 minutes – helps it get through the vagina (cause it's so acidic) Clotting proteins from seminal vesicles After 10-20 mins, semen re-liquifies PSA and proteolytic enzymes from prostate gland This occurs to protect sperm cells from the acidic vaginal environment The Penis: Functions of the Penis Two functions: 1. Conducts urine to the exterior 2. Introduces semen into the vagina during sexual intercourse Regions and Structures of the Penis Root of the Penis Fixed portion that attaches the penis to the body wall just inferior to the pubic symphysis Consists of 2 parts: 1.Bulb Expanded, posterior continuation of corpus spongiosum 2.Crura 2 separated, tapered portions of corpora cavernosa Body Shaft of the penis Tubular, movable portion of the organ Glans penis (head) Expanded distal end that surrounds the external urethral orifice Neck of glans Narrow portion between the shaft and the glans Erectile tissue The body is composed of three erectile tissue masses: 1.Corpora cavernosa Two cylindrical masses on the dorsal surface of the penis 2.Corpus spongiosum Surrounds the penile urethra Expands at the tip of the penis to form the glans Three-dimensional network with vascular spaces (sinusoidal spaces) In the resting state, arterial branches are constricted, and muscular partitions are tense (restricts blood flow into the erectile tissue) Phases in the Male Sexual Response: 1. Arousal Erotic thoughts or stimulation of sensory nerves in the genital region increase parasympathetic stimulation through pelvic nerves Release of nitric oxide causes arterial dilation Blood flow increases, engorging vascular channels Veins become compressed, and blood is trapped Erection of the penis occurs 2. Emission or ejaculation Caused by sympathetic activation Begins with peristaltic contractions in the ampullae of the ductus deferens Pushes sperm into the prostatic urethra Contractions continue in the seminal glands and prostate Secretions from these glands mix with sperm to form semen Impotence or erectile dysfunction (ED) Inability to achieve or maintain an erection Various causes Vascular changes (low blood pressure) Interference with neural commands (autonomic nervous system) Psychological factors (depression, anxiety) Medications (viagra and cialis) temporarily inactivate enzymes that oppose nitric oxide (NO) Small amounts of NO can then produce erection Hormones and the Male Reproductive System: Hormonal Regulation Hypothalamus Secretes gonadotrophin-releasing hormone (GnRH) - released at a steady rate and pace Targets the anterior lobe of the pituitary gland Anterior lobe of the pituitary Responds by producing two gonadotropins - Luteinizing hormone (LH) - Follicle-stimulating hormone (FSH) Luteinizing Hormone (LH) Targets the interstitial cells of the testes (Leydig Cells) Interstitial cells secrete testosterone and other androgens Testosterone levels are regulated by negative feedback High testosterone level inhibits release of GnRH Follicle-stimulating Hormone (FSH) Targets nurse cells (sertioli cells) of seminiferous tubules Nurse cells (sertioli cells) Promote spermatogenesis and spermiogenesis Secrete androgen-binding protein (ABP) - binds testosterone and keeps in area of developing sperm (required for spermatogenesis – testosterone) - stimulates maturation of spermatids Secrete inhibin - inhibits FSH - provides feedback control of spermatogenesis Testosterone Principal androgen Synthesized from cholesterol Released by interstitial cells (Leydig cells) Lipid soluble Moves from interstitial cells, to interstitial fluid, to blood Controlled by negative feedback Supresses GnRH & LH External genitalia & prostate transform testosterone to DHT (dihydrotestosterone) Effects of Testosterone Prenatally Testosterone stimulates development of male reproductive system & descent of testes DHT stimulated development of external genitals In brain testosterone converted to estrogens, which support some parts of brain development Puberty Enlarge male sex organs, spermatogenesis, sex drive Anabolic – stimulates protein production Secondary sex characteristics - facial & chest hair - muscle/bone enlargement - increase sebaceous gland secretion - laryngeal enlargement After Puberty Maintains libido (sexual drive) and related behaviours Stimulates bone and muscle growth Maintains male secondary sexual characteristics Maintains accessory glands and organs of the male reproductive system Female Reproductive System: Female Reproductive System: Functions Produces sex hormones Produces functional gametes Protects and supports developing embryo Maintains growing fetus Nourishes newborn infant Female Reproductive Anatomy: Female External Genitalia Vulva Outer genitals Urethra Where urine comes out of Mons pubis Pad of fatty tissue overlapping symphysis pubis Clitoris Contains erectile tissue Labia Contain glands that lubricate the entrance to the vagina Female Internal Genitalia Ovaries Uterine tubes Uterus Vagina Mammary gland of breast Produces milk to nourish infant Female Gonads Ovaries Produce gametes (oocytes that mature into ova) Produce hormones Female Reproductive Tract Uterine tubes/fallopian tubes Deliver oocyte or embryo to the uterus Normal sites of fertilization Uterus Site of embryonic and fetal development Also site of exchange between maternal and embryonic/fetal bloodstream Vagina Birth canal during delivery Passageway for fluids during menstruation Ovaries: Paired almond-shaped organs near the lateral wall of the pelvic cacity Three main functions: 1. Oogenesis: production of immature female gametes (oocytes) 2. Secretion of female sex hormones - estrogen and progesterone 3. Secretion of inhibin - inhibits FSH production in the anterior pituitary gland Ligaments Ovaries are held in place by various ligaments Ovarian ligament Extends from uterus to medial surface of ovary Mesovarium Fold of mesentery; supports and stabilizes ovary Suspensory ligament Extends from lateral surface of ovary to pelvic wall Broad ligament Extensive mesentery enclosing ovaries, uterine tubes, and uterus Attaches to sides and floor of pelvic cavity Layers of the Ovaries: Germinal epithelium Layer of squamous or cuboidal cells covering the ovary Continuous with the visceral peritoneum Coveres the entire ovary – outer layer Tunica albuginea Dense connective tissue layer just deep to the germinal epithelium Inferior of the ovary Cortex (superficial layer holding follicles where oocytes are produced) - outer ring (oocytes form here) Medulla (Deep to the cortex, loose CT w/ blood vessels) - inner portion (houses blood) Cortex: Contains: ovarian follicles & dense irregular CT Ovarian follicles A developing oocyte surrounded by one or more layers of cells called follicular cells oocyte is just the egg, follicle is the tissue surrounding the egg Mature follicles (Graafian Follicles) Large, fluid filled follicle that is ready to rupture its secondary oocyte (ovulation) Corpus Luteum Remnants of follicle after ovulation that produces progesterone, estrogens, relaxin & inhibin until it degerates into scar tissue (copus albicans) Corpus luteum = "yellow body" Oogenesis and the Ovarian Cycle: Oogenesis Formation and development of the oocyte Occurs inside a follicle Begins before birth, accelerates at puberty, ends at menopause Nuclear events are very similar as with spermatogenesis Ovarian cycle Development of the follicle Occurs along-side of oogenesis Development ends in the rupture of mature follicle (ovulation) Becomes the corpus luteum and eventually corpus albicans Oogenesis: Begins in early fetal development in females Step 1: Primordial germ cells migrate from yolk sac to ovaries Germ cells differentiate into oogonia (2n) that continue to divide miotically to produce millions of germ cells Before birth, most of these germ cells degenerate through atresia A few develop into primary oocytes (2n) Step 2: Beginning b/w 3rd and 4th month of fetal development, primary oocytes enter meiosis Arrest in prophase of meiosis during fetal development During this time, it is surrounded by one later of follicular cells and is called a primordial follicle Stay here until puberty 200,000 – 2 million present at birth 40,00 remain at puberty About 500 oocytes are ovulated over life time More are lost to atresia Less than 10,000 eggs at menopause, non-functional Step 3: Starting at puberty and ending at menopause Each month, follicle stimulating hormone (FSH) from anterior pituitary stimulates some of the primary oocytes to complete meiosis I Yields haploid secondary oocytes and a polar body Secondary oocyte gets the majority of cytoplasm Step 4: These secondary oocytes begin meiosis II but are arresting in metaphase II One (usually) secondary oocyte is released (ovulated) per month Step 5: At fertilization, the secondary oocyte divides into a second polar body and mature ovum (both haploid) The Ovarian Cycle: Occurs alongside oogenesis Involves changes in ovarian follicles Specialized structures where oocyte growth and meiosis I occur About 2 million primordial follicles exist at birth Each containing a primary oocyte At puberty, only about 400,000 primordial follicles remain Others degenerated in a process called atresia Each month, FSH stimulate the development of several follicles And development of the oocyte inside along with it (oogenesis) Two stages: 1. Follicular phase – development of the follicle 2. Luteal phase – development of the corpus luteum Stage 1: Primordial follicle in egg nest Primordial follicle Inactive primary oocyte surrounded by a simple squamous layer of follicle cells Egg nests Clusters of primary oocytes in the outer portion of the ovarian cortex, near the tunica albuginea Stage 2: Formation of primary follicles Follicular cells enlarge, divide, and form several layers around the primary oocyte Follicular cells now called granulosa cells Zona pellucida (pellucidus, translucent) – region that develops around the oocyte Thecal endocrine cells (theca, box) – layer of cells that form around the follicle Thecal cells and granulosa cells work together to produce estrogen Stage 3: Formation of secondary follicles Follicle wall thickens, and follicular cells secrete fluid Fluid filled pockets expand and separate the inner and outer layers of the follicle Stage 4 & 5: Formation of tertiary follicle Occurs about day 10 – 14 of cycle One secondary follicle becomes a tertiary follicle and eventually a mature graafian follicle Expanded central chamber (antrum) is filled with follicular fluid – oocyte projects into the antrum Granulosa cells form a protective layer (corona radiata) around the secondary oocyte Stage 6: Ovulation Mature follicle releases secondary oocyte and corona radiata into the pelvic cavity Occurs around day 14 of an average 28 day cycle Marks end of follicular phase and start of luteal phase Fimbrae sweep them into uterine tube If no fertilization, cells degenerate Stage 7: Formation of corpus luteum Empty tertiary follicle collapses Remaining granulosa cells proliferate Secrete estrogen and progesterone Progesterone stimulates maturation of the uterine lining Stage 8: Formation of corpus albicans Knot of pale scar tissue produced by fibroblasts Formed by degeneration of the corpus luteum when fertilization does not occur after 12 days Marks the end of the ovarian cycle Uterine Tube Expanded funnel opens into the pelvic cavity along the surface of the ovary Other end opens into the uterine cavity Uterus Inferior to the ovaries Usually angled anteriorly above the urinary bladder Vagina Extends from the uterus base (cervix) to the exterior External genitalia Clitoris Stimulation produces pleasurable sensations associated with female orgasm Labia Labia majora Labia minora Uterine Tubes (Fallopian Tubes or Oviducts): Bilaterally, extend 10 cm from uterus and lie within folds of broad ligament Passage for sperm to meet ovum, and fertilized ovum to reach uterus Sections of the Uterine Tubes: Infundibulum Funnel shaped portion near the ovary, open to pelvic cavity Fimbrae are moving, finger like projections that sweep secondary oocyte from peritoneal cavity into the uterine tube Ampulla Central region Isthmus Narrow portion that joins the uterus Uterine Tube Histology Mucosa Epithelial cells - ciliated simple columnar cells move fertilized ovum (or secondary oocyte) to uterus - non-ciliated peg cells (w/ microvilli) secrete fluid that nourishes ovum Lamina propria Muscularis 2 layers of muscle that provide peristaltic movement for fertilized ovum Serosa Uterine Tube and Fertilization Sperm and secondary oocyte generally meet in ampulla of uterine tube Fertilization can occur up to 24 hours after ovulation Few hours after fertilization, nuclei of ovum & sperm unite Fertilized diploid zygote (2n) starts cell divisons as it moves toward uterus 6 – 7 days after fertilization, zygote arrives in uterus Uterus: Hollow, muscular organ Between urinary bladder & rectum Size & shape of an inverted pear Functions Pathway for sperm deposited in vagina to reach uterine tubes Site of implantation of fertilized ovum Site of fetal development Source of menses released during menstruation Contractions in the muscular wall are important in delivering the fetus at birth Uterus Anatomy: Fundus Dome shaped superior portion Body Tapering central portion Interior = uterine cavity Isthmus Constricted portion between body and cervix Cervix Inferior narrow portion that opens to vagina Interior = cervical canal Opens to uterine cavity at internal os Opens to vagina at externa os Uterus Histology: Layers Perimetrium Serosa, part of visceral peritoneum Myometrium 3 layers of smooth muscle Endometrium columnar epithelium Stratum functionalis Lines uterine cavity, sloughs off during menstruation Stratum basalis Permanent & gives rise to new stratum functionalis after each menstruation Uterine Vasculature Spiral Arteries Supply the stratum functionalis Constriction due to hormonal changes initiate menses This is where the blood of menses come from Uterine Secretions Secretory cells in cervical mucosa produce mucous Water, glycoproteins, serum-type proteins, lipids, enzymes, inorganic salts Thin secretions: more receptive to sperm & supports capacitation Thick secretions: forms cervical plug that physically impedes sperm Cervix & mucous protect sperm from hostile environment of vagina & uterus Uterine Ligaments Round ligament Attach anterior of uterus to labia majora to maintain anteflexion of uterus Common source of pain during pregnancy Uteralsacral ligaments Connect uterus to sacrum on either side of rectum Vagina: Elastic, muscular tube Extends from the cervix to the vestibule (space bordered by the labia minora) Between urinary bladder & rectum Variable diameter (highly densible) Internal passageway is the vaginal canal Reproductive Functions of the Vagina 1. Passageway for menstrual fluids 2. Receives and holds sperm during sexual intercourse prior to the passage into the uterus 3. Forms inferior portion of birth canal Anatomical Regions of the Vagina Vaginal canal Internal passageway Lined by nonkeratinized stratified squamous epithelium Fornix Shallow recess in the vagina surrounding the tip of the cervix Rugae Folds formed by the vaginal lining when relaxed Hymen Elastic epithelial fold that usually partially blocks entrance to the vagina Frequently absent Stretched or torn during intercourse, tampon use, or heavy physical exercise Vaginal Histology Mucosal layer Stratified squamous epithelium & areolar CT Large store of glycogen break down to create an acidic environment (alkaline components of semen neutralize) Continuous with uterine mucosa, has folds = rugae Mucosa dendritic cells = APC (antigen presenting cells) Muscular layer Smooth mm that allows for considerable stretch Adventitia Loose CT that binds to other organs Vulva: Also called the pudendum It is the female external genitalia The External Genitalia includes: Mons pubis Fatty pad over pubic symphysis Labia majora & Labia minora Folds of skin encircling vestibule Vestibule Area between the labia minora where vaginal & urethral orifices are found Hymen Elastic epithelial fold that usually partially blocks entrance to the vagina Clitoris Small mass of erectile tissue comparable to the corpora carvernosa and corpus spongiosum of the penis Highly innervated and plays major role in orgasm during intercourse Bulb of the Vestibule Masses of erectile tissue deep to labia on either side of vaginal orifice Greater Vestibular (Bartholin's) glands Activated during sexual arousal Lesser Vestibular (Skene's) glands Secrete onto the vestibular surface, keeping it moist Perineum: Diamond shaped area between thighs and buttocks of males and females Contains external genitals & anus Bounded by pubic symphysis and coccyx Urogenital triangle External genitals Anal triangle Anus Mammary Glands: Provide nourishment (milk) for developing infant Milk production (lactation) controlled by hormones released by the reproductive system and the placenta Located on the anterior chest, directly over the pectoralis major muscle Embedded in the subcutaneous tissue of the pectoral fat pad deep to the skin Hormone: prolactin (high during and after pregnancy) Suspensory Ligaments of the Breast Bands of dense connective tissue Surrounds the duct system and form partitions between lobes and lobules Lobes Glandular tissue divided into lobes Each lobe has several secretory lobules Each lobule is composed of secretory alveoli Modified sudoriferous glands (apocrine sweat) Ducts from the lobules converge into one lactiferous duct per lobe Each lactiferous duct expands near the nipple to form a lactiferous sinus Structures: Nipple Conical projection where 15 – 20 lactiferous sinuses open onto the body surface Areola Reddish-brown skin around the nipple Grainy texture from sebaceous glands deep to the surface Lecture 3: The Female Reproductive Cycle: There are two cycles within the female reproductive cycle 1. Ovarian cycle Events that occur during & after an oocyte maturation Focused on the changes in the follicle (follicular phase and luteal phase) 2. Uterine cycle (menstrual cycle) Changes in endometrium in preparation of fertilized ovum Regulation of the Ovarian (and Uterine) Cycle Ovarian and uterine cycle are controlled by cyclical changes in hormones The two cycles must operate synchronously for proper reproductive function All coordinated by GnRH from the hypothalamus Steps: Step 1: Begins with the release of gonadotrophin-releasing hormone (GnRH) From hypothalamus Causes production and secretion of FSH and LH Cyclical rise in GnRH creates cycle Ovaries Produce hormones + reproductive stuff Step 2: Follicular phase of the ovarian cycle Oogenesis: Begins when FSH stimulates some follicles to become tertiary follicles Begin development in utero Oogonia differentiate into primary oocytes As follicles develop, FSH levels decline Primary oocytes stop in meiosis I until puberty as a result of negative feedback effects of inhibin - secreted by the follicle Puberty ---> mid meiosis II Either fertilized or shed Developing follicles also secrete estrogens low lvls of estrogens inhibit LH secretion Ovarian cycle: Follicular cell + primary oocyte = primordial follicle inhibition decreases as estrogen levels climb Primordial follicle ---> granulosum cells Granulosum cells + thecal cells = primary follicle estrogen decreases basal body temperature about 0.3 C lower than during the luteal phase (estrogen makes people Primary follicle ---> secondary follicle colder) Secondary follicle ---> tertiary follice (antrum – pocket of fluid) Tertiary follicle ---> Graffian follicle/ mature follicle Step 3: Ovulation Graffian follicle/ mature follicle ---> crack it open and there is a secondary oocyte in there ----> corpus GnRH and elevated estrogen levels stimulate LH secretion luteum (produces hormones – estrogens and progesterone) ----> corpus albicans Massive surge in LH on or around day 14 triggers: Completion of meiosis I by the primary oocyte Forceful rupture of the folliclular wall Ovulation (~9 hours after LH peak) Formation of corpus luteum Luteal phase begins after ovulation Mittelschmerz Pain from follicular swelling, ovarian wall rupture, small amount of blood leaking into pelvic cavity surrounding ovulation Step 4: Luteal phase Corpus luteum secretes progesterone Stimulates and sustains endometrial development Progesterone levels increase and estrogen levels fall Suppresses GnRH If pregnancy does not occur Corpus luteum lasts 2 weeks Stops secreting hormones & degenerates into corpus albicans If pregnancy does occur Early cells of the placenta produces hCG It rescues corpus luteum to keep it alive & it continues secretory functions Hormones: Follicle Stimulating Hormone (FSH) Source Secreted from anterior pituitary Stimulation In response to GnRH from the hypothalamus Inhibition (stops it) Inhibin from granulosa cells and corpus luteum Estrogen Functions Initiates follicle growth Stimulates ovarian follicles to release estrogen and inhibin Lutenizing Hormone (LH) Source Secreted from anterior pituitary Stimulation Production by GnRH, secretion by estrogen and GnRH Inhibition (stops it) Inhibin from granulosa cells and corpus luteum Functions Trigger ovulation Promote formation of corpus luteum Stimulates corpus luteum to produce estrogens, progesterone, relaxin & inhibin Estrogen Made from cholesterol 3 types: Estradiol, estrone, estriol Source Granulosa cells, theca cells, then corpus luteum Stimulation FSH and LH Functions Triggers release of LH (LH surge) Develop and maintain secondary sex characteristics Adipose deposit: breast, hips, mons pubis Broad pelvis Hair growth on head, pubic, axillae Causes a postive feeback Increase protein anabolism Decreases osteoclast activity Progesterone Made from cholesterol Source Corpus luteum Stimulation LH The follicle stops FSH to be released Cause theres and increase of estrogen and inhibin (negative feedback) Functions Prepares endometrium for implantation Prepares mammary glands for milk secretion Inhibin Source Granulosa cells then corpus luteum Stimulation FSH and LH Functions Inhibits FSH & LH secretion Relaxin Source Corpus luteum then placenta (if implantation occurs) Stimulation LH Functions Relaxes myometrium – the uterine muscle Relaxes pubic symphysis & dilates cervix during pregnancy The Uterine (Menstrual) Cycle: The uterine cycle is the changes in endometrium in preparation of fertilized ovum There are three phases of the uterine cycle 1. Menstruation (menses or "period") 2. Proliferative phase 3. Secretory phase 1. Menstruation Day 1 – 7 (day 1 is the first day of bleeding) Uterine changes Decreased progesterone & estrogen = spiral arteries constrict and cells die Entire stratum functionalis sloughs off Leaves 2 – 5 mm of stratum basalis is left Whats happening in the ovaries? FSH influences primordial follicles to develop into primary, then secondary follicles Can take several months, so a follicle that starts development at the beginning of a cycle, may not be mature until many months later 2. Proliferative Phase Day 7 – 14, but variable Uterine changes Estrogen from growing follicles build endometrium Stratum basalis undergoes mitosis to produce stratum functionalis Endometrial glands & arterioles grow and develop Whats happening in the ovaries? Secondary follicles in ovaries begin secreting estrogen & inhibin Usually dominant follicle becomes the mature follicle and enlarges until ready for ovulation Increases estrogen production 3. Secretory Phase Day 15 – 28, but variable Uterine changes Progesterone & estrogen from corpus luteum cause: Endometrial glands to grow & secrete glycogen – stimulated by progesterone Endometrium to vascularize (increase in spiral artery size) & thicken Uterus is ready for a fertilized ovum to arrive If no fertilization Corpus luteum degenerates & progesterone & estrogen production declines and begins the menstrual phase Whats happening in the ovaries? LH promotes formation of corpus luteum Stimulated by LH, corpus luteum secretes estrogens, progesterone, relaxin & inhibin If pregnancy does not occur Corpus luteum lasts 2 weeks Stops secreting hormones & degenerates into corpus albicans If pregnancy does occur Early cells of the placenta produces hCG It rescues corpus luteum to keep it alive & it continues secretory functions Pregnancy & Labour: Cleavage Rapid division of cells to create multiple cells Happens on the journey to the uterus Implantation Day 7 Starts around day 7 Start the formation of the placenta Begins with the attachment of the blastocyst to the uterine endometrium Blastocyst erodes endometrial lining and becomes enclosed within the endometrium by day 10 Trophoblast cells invade and become syncytiotrophoblasts Eventually forms the placental membrane Inner cell mass becomes embryo Day 9 Around day 9, amniotic cavity forms Amniotic cavity is formed from the placenta Filled with amniotic fluid Protects and supports embryo Amniocentesis is usually carried out between the 15th and 20th weeks of pregnancy Testing cells in the amniotic fluid Day 10 Around day 10, implantation finishes and the yolk sac forms Site of early hematopoiesis from stem cells - week 3 – 8 Gives nutrients to developing fetus prior to placental formation The Placenta: Fully formed and functional around week 12 Site of exchange between maternal blood and fetal blood Blood supply Umbilical arteries Carry blood from the developing fetus to the placenta Blood is deoxygenated and full of waste products Chorionic villi Provide surface area for exchange of gases, nutrients, and waste between fetal and maternal bloodstreams Umbilical vein Carries blood from the placenta to the fetus Blood contains nutrients and oxygen Contains wartons jelly – stem cells Hormone Production from the Placenta Human chorionic gonadotropin (hCG) Maintains corpus luteum until about week 12 Human placental lactogen (hPL) Aka prolactin Helps prepare mammary glands for milk production Relaxin Relaxes myometrium Relaxes pubic symphysis & dilates cervix during pregnancy Estrogen & Progesterone Takes over progesterone production from corpus luteum at 12 weeks Maintains uterine lining During third trimester, rising estrogen plays a role in stimulating labour and delivery Multiple Births: Dizygotic ("fraternal") twins Develop when two separate oocytes are ovulated and fertilized 70 % of twins are dizygotic Monozygotic ("identical" or "maternal") twins Result from separation of blastomeres early in cleavage Glycogen – for energy, the embryo needs energy to grow Can also result when inner cell mass splits before gastrulation Genetic makeup of twins is identical (both formed from the same set of gametes) Changes During Pregnancy: Uterus ascends to the abdominal cavity The abdominal contents displaced in response to the increased size of the uterus GERD and increased urination are possible results Enlarged mucus glands of the cervix during pregnancy secrete a mucus which forms a plug Acts as a seal for the uterus and protects it from ascending infection Fluid retention can compress nerves passing through narrow canals, such as the carpal tunnel, causing pain, numbness and weakness in the hand Cardiac output increases to meet increased demand Up to 30 – 50% of baseline Estrogen mediates this rise in cardiac output by increasing the pre-load and stroke volume, mainly via a higher overall blood volume Up to 40 – 50% The heart rate increases, but generally not about 100 beats/minute The diaphragm is elevated by about 4cm due to the enlarged uterus Ligaments connecting ribs to sternum become lax during pregnancy Leads to increased tidal volume (30 – 50%) Respiratory rate increases by 1 – 2 breaths more than normal Pigmentation changes occur during pregnancy include darkening of: Areolar on the breast Linea nigra Increased facial pigmentation Stretch marks (striae gravidarum) occur on the abdomen, breast, thighs and buttocks to varying degrees Enlargement under the influence of relaxin, progesterone and estrogen, prolactin, and hPL Breast tenderness is common in the early stages of pregnancy Montgomery's tubercles developing form enlarging sebaceous glands around the areolar Protect nipple from cracking Nipple gets darker and bigger – so baby can see it