Reproductive Male

  • Testes (within the scrotum) produce sperm
  • Sperm delivered to exterior through a system of ducts (epididymis, ductus deferens, ejaculatory duct, urethra)
  • Sperm need cooler temps (3 degrees Celsius colder than body), that’s why testes are held away from the body
  • Secondary sex characteristics (driven by testosterone)
  • Develop at puberty to attract a mate
  • Pubic/axillary/facial hair
  • Scent glands, body morphology, low pitched voice
  • The Scrotum
  • Sac of skin and superficial fascia
  • Hangs outside the abdominopelvic cavity
  • Contain paired testes
  • Temp is kept constant by:
  • Smooth muscles that wrinkles scrotal skin (dartos muscle), hot: stretch out to increase heat absorption/dissipation
  • Bands of skeletal muscle that elevate the testes (cremaster) hot: testes move away from body
  • Pampiniform Plexus: cools arterial blood as it enters the testes, warms venous blood leaving the testes
  • The Testes
  • Septa divide the testis into 250-300 lobules, each containing 1-4 seminiferous tubules (site of sperm production, more of them, more sperm being made)
  • Blood supply: testicular arteries/veins
  • Spermatic Cord encloses: nerve fibers, blood vessels, lymphatics
  • Sertoli cells: nurse sperm, prevent immune system from becoming sensitive to developing sperm by forming blood-testis barrier
  • Leydig cells: produce testosterone
  • Spermatic Ducts:
  • Epididymis (head, body, tail)
  • 6 m long coiled duct
  • Site of sperm maturation and storage (fertile for 60 days)
  • Ductus (Vas) Deferens
  • 45 cm long
  • Peristalsis during orgasm
  • Contraction to get out as much fluid as possible
  • Ejaculatory duct
  • 2 cm
  • Accessory Glands
  • Seminal Vesicles
  • Viscous, alkaline seminal fluid
  • 70% of semen
  • Prostate
  • Milky, slightly acidic fluid
  • Contains citrate and enzymes
  • Plays a role in activation of sperm
  • Bulbourethral Glands
  • Prior to ejaculation- thick, clear mucus
  • Lubricates the glans penis
  • Neutralizes traces of acidic urine in urethra
  • Semen
  • Mixture of sperm and accessory fluid
  • Contains nutrients
  • Protects and activates the sperm
  • Facilitates sperm movement
  • Prostaglandins in semen (decrease viscosity of mucus in cervix, stimulate reverse peristalsis in uterus)
  • Alkalinity neutralizes acid in male urethra and female vagina
  • Antibiotic chemicals destroy certain bacteria
  • Only 2-5 ml of semen are ejaculated
  • Males never lose ability to make sperm
  • Females have all ova at birth, will never make any more
  • Sertoli Cells (sustentacular)
  • Nourish developing spermatozoa
  • Intracellular junctions from blood-testes barrier (super tight)
  • Produce inhibin, which represses FSH
  • Secretes androgen-binding protein (ABP), which binds testosterone and keeps concentration of testosterone in testes
  • Leydig Cells (interstitial)
  • Secrete androgens: testosterone, dihydrotestosterone, androstenedione, dihydroepiandrosterone
  • Sperm Cells
  • Tip of the head is called an acrosome, burrows into egg to get sperm to egg, DNA
  • Middle part- mitochondria to get energy to swim
  • Tail: can have defect
  • Genetic, metabolic, locomotor regions
  • Spermatogenesis
  • Begins at puberty, and then just keeps going- by mitosis
  • Type A daughter cell: remains at basal lamina to produce more sperm
  • Type B gets pushed toward lumen where it becomes a primary spermatocyte
  • Then meiosis happens, and meiosis 1 occurs to each primary spermatocyte to form secondary spermatocytes
  • Meiosis 2 happens and forms fourspermatids
  • Spermiogenesis (forms mature sperm)
  • Happens all the time
  • Takes 24 days
  • Makes the spermatid elongate, sheds its excess cytoplasmic baggage, and forms a tail
  • Results in a spermatozoon
  • Testicular Hormones
  • Leydig: FSH increases LH receptor number
  • Leydig: LH increases testosterone (T) synthesis
  • Sertoli: FSH stimulates production of ABP
  • ABP binds T, thus increasing concentration in testes
  • Increased T stimulates spermatogenesis
  • Testosterone
  • Differentiation of fetal male internal genetalia
  • Spermatogenesis
  • Development of secondary sexual characteristics
  • Libido
  • Muscle development, skeletal growth
  • Red blood cell production
  • Anabolic Steroids
  • Exogenous hormone, mimics hyper secretion
  • Negative feedback effect on pituitary results in decreased LH secretion
  • Infertility, testicular atrophy, impotence
  • Trenbelone has androgenic properties and is used in feedlots to help build muscle, too much can make him infertile
  • Hypothalamic-Pituitary-Gonadal Axis
  • 1. Hypothalamus releases GnRH, which stimulates production of LH/FSH
  • 2. GnRH binds to pituitary cells, prompting them to secrete FSH and LH into the blood
  • 3. FSH simulates spermatogenesis indirectly by stimulating sertoli cells to release ABP, which keeps levels of T high
  • 4. LH binds to leydig endocrine cells in seminiferous tubules, prodding them to secrete T, rising T levels triggers spermatogenesis
  • 5. Testosterone stimulates a lot of effects on males
  • 6. Rising T levels inhibits GnRH, LH/FSH production
  • 7. Inhibin made by sertoli cells, when sperm count is high, more inhibin is released to inhibit release of GnRH and FSH, and vice versa with low sperm count

Reproductive Female

  • Functions
  • Produce and deliver gametes
  • Provide nutrition and room for fetal development
  • Give birth
  • Nourish infant
  • Female Duct system
  • Uterine tubes, uterus, vagina
  • External genitalia
  • Clitoris, labia minora, labia majora
  • Accessory glands beneath skin provide lubrication
  • Females born with set number of oocytes at birth (2 million400 being ovulated)
  • Oocyte in follicular structure- need granulosa cells to survive
  • Antrum (blue ponds) large space filled with follicular fluid
  • CL produces progesterone
  • Uterine Tubes
  • Ampulla: usual site of fertilization
  • Ciliated fimbriae of infundibulum create currents to move oocyte into uterine tube
  • Isthmus: constricted region where tube joins uterus
  • Oocyte is carried along by peristalsis and ciliary action
  • Nonciliated cells nourish the oocyte and the sperm
  • Uterus
  • Cervix: narrow neck that projects into the vagina
  • 10 cm dilated before birth
  • Fundus: rounded superior region
  • Isthmus: narrowed inferior region
  • Cervical glands secrete mucus, which block sperm entry except during midcycle
  • Vagina
  • Birth canal and organ of copulation
  • Extends between the bladder and the rectum from the cervix to exterior
  • Urethra embedded in anterior wall
  • Oogenesis and the Sexual Cycle
  • Sexual Cycle: events recurring every month when pregnancy does not occur
  • Ovarian cycle: events in ovaries
  • Menstrual/estrous cycle: parallel changes in uterus
  • Reproductive Cycle: events occurring between fertilization and birth
  • Ovarian Cycle
  • Monthly series of events associated with the maturation of an egg
  • Two consecutive phases (in a 28 day cycle)
  • Follicular phase: period of follicle growth (days 1-14: which is about at ovulation)
  • Technically ovulation occurs midcycle
  • Luteal phase: period of corpus luteum activity
  • LH critical for ovulation (day 14-28)
  • Follicular Phase
  • 1. Primordial follicle enlarges and becomes a primary follicle
  • Squamouslike cells become cuboidal
  • 2. Primary follicle becomes secondary follicle when more than one cell layer is present, these are called granulosa cells
  • These granulosa cells and oocyte guide each other’s development, if one dies, so does the other
  • 3. Secondary follicle becomes late secondary follicle
  • Fluid begins to accumulate
  • Zonapellucida forms around the oocyte for protection
  • A layer of connective tissue and epithelial cells condenses around the follicle, forming the theca folliculi, which helps to produce estrogens
  • 4. Late secondary follicle becomes a vesicular follicle
  • An antrum forms and expands to isolate the oocyte with its corona radiata on a stalk
  • Vesicular follicle bulges from external surface of the ovary
  • Primary oocyte completes meiosis 1 to form the secondary oocyte and first polar body (one oocyte, once a month)
  • Very few get to this point
  • Ovulation
  • Ovary wall ruptures and expels the secondary oocyte with its corona radiata
  • Mittelschmerz: twinge of pain sometimes felt at ovulation
  • 1-2% of ovulations release more than one secondary oocyte, which, if fertilized, results in fraternal twins
  • Luteal Phase
  • Lutenization: driven by LH, formation of corpus luteum
  • Yellow body is the CL
  • Ruptured follicle collapses
  • Granulosa cells and internal thecal cells form corpus luteum
  • Corpus luteum secretes progesterone and estrogen
  • Target LH to synchronize herds, causes lysis of CL and sets all cows anew
  • If no pregnancy occurs, the C: degenerates into a CA in 10 days
  • If pregnant, CL produces hormones until placenta takes over at about 3 months
  • Follicular Maturation
  • 1. Mitotic division of primordial germ cells (pre-natal)
  • 2. Nuclear Arrest
  • 3. Cytoplasmic growth (cytoplasm of oocyte growing)
  • Resumption of meiosis (meiosis 2 only happens if sperm reaches egg)
  • Uterine (Menstrual/Estrous) Cycle
  • Cyclic changes in endometrium in response to ovarian hormones
  • Three phases
  • 1. Days 1-5: menstrual/resorbtion phase
  • 2. Days 6-14: proliferative (preovulatory) phase
  • 3. Days 15-28: secretory (postovulatory) phase (constant 14 day length, uterine wall secretions)
  • If pregnant, retain endometrial lining, if not, menstruation
  • Menstrual Phase
  • Ovarian hormones are at their lowest levels
  • Gonadotropins beginning to rise (FSH/LH)
  • Stratum functionalis is shed and bleeding occurs
  • By day 5, growing ovarian follicles start to produce more estrogen
  • Proliferative Phase (follicles are getting bigger/follicular phase)
  • Estrogen levels prompt generation of new functional layer and increased synthesis of progesterone receptors in endometrium
  • Glands enlarge and spiral arteries increase in number
  • Ovulation occurs at the end of this phase in response to LH surge, which causes a CL to form
  • High estrogen levels thins out cervical mucus to allow passage of the sperm
  • Secretory Phase
  • Progesterone levels prompt further development of endometrium, glandular secretion of glycogen, formation of cervical mucus plug
  • If fertilization has not occurred
  • CL degenerates
  • Progesterone levels fall
  • Spiral arteries kink and spasm
  • Endometrial cells begin to die
  • Rush of blood fragments weakened capillary beds and the functional layer sloughs
  • Two Cell Model
  • FSH stimulates the initial steps in estrogen formation in granulosa cells (granulosa cells alone cannot produce estrogen)
  • LH: stimulates thecal cells (which makes testosterone, which is converted to estradiol in granulosa cells, which eventually helps make estrogen
  • Without LH, no ovulation
  • Without estrogen (made from follicles), no LH surge
  • Lutalyze: helps cause the lysis of the CL to synchronize herd
  • Matrix: progesterone, makes the brain think the animal is pregnant, CL still degenerates and brain does not activate cyclicity
  • Functions/Target of E2/Estrogen
  • Target: repro system
  • 1. Vaginal mucous increased
  • 2. Increased blood flow (more hormones everywhere)
  • 3. Genital swelling (swollen vulva)
  • 4. *Growth of uterus*
  • Menstruation in mammals
  • Loss of endometrial lining through blood flow limited to primates, other species absorb the lining
  • One gamete has motility (Sperm), which is the parent producing sperm considered male, can have Y chromosome
  • One gamete contains nutrients for developing zygote (egg), female also provides shelter for developing fetus (uterine and placenta)
  • 2 Meiotic Divisions
  • 1. Begins in fetal development (making of primordial follicles), completed at the time of ovulation
  • 2. Occurs at fertilization, very few follicles complete both phases
  • Cell divison without replication, 46 diploid-23 haploid
  • How does CL know to stay on ovary?
  • Makes Maternal Recognition of Pregnancy
  • Cow: Interferon Tau
  • Pig: Estrogen
  • Horse: Conceptus/unknown protein
  • Human: Human chorionic gonadotropin
  • Secreted by blastocyte within 9 days of conception
  • Prevents death of CL
  • Detected by pregnancy tests
  • Causes morning sickness
  • How does sperm get through to egg?
  • 1. Aided by surface enzymes, sperm cell weaves past granulosa cells of the corona radiata
  • 2. Binding of sperm to ZP3 molecules in zonapellucida causes a rise in Ca2+ level within the sperm, causing acrosomal reaction
  • 3. Acrosomal enzymes digest holes through zonapellucida, clearing a path to the oocyte
  • 4. Sperm forms an acrosomal process, which binds to the oocytes sperm-binding receptors
  • 5. The sperm and oocyte plasma membranes fuse, allowing sperm contents to enter oocyte
  • 6. Entry of sperm causes a rise in Ca2+ levels in oocyte cytoplasm, trigging cortical reaction, which hardens the zonapellucida and clips off sperm receptors to block more sperm getting in
  • Organ development0 between 7-9 weeks is when you can tell sex of baby
  • Males
  • Testosterone promotes development of Wolffian ducts
  • Mullerian inhibiting substance (made by sertoli cells), causes regression of Mullerian ducts
  • Females
  • Absence of MIS causes Mullerian ducts to proliferate and form uterus, uterine tubes, and upper 2/3 of vagina
  • Absence of androgens (Testosterone), causes Wolffian ducts to degenerate

Repro in a cow/pig/whatever livestock animal you want to say

  • Anestrus: female is not cycling
  • Cows have 21 day estrous cycle:
  • Proestrus (day 17-20/follicular phase):
  • Prior to estrus, CL is undergoing regression which means low levels of progesterone, which allows final follicular development
  • Tertiary follicles/oocytes undergo final maturation, estrogen levels increase, one dominant follicle that is stimulated to final maturation by FSH/LH
  • Female starts to become receptive (pheromones-bull will follow one in heat around)
  • Estrus: (day of standing heat/day 0 of estrus cycle)
  • Female is in heat
  • LH surge causes ovulation (occurs during metestrus in cow, estrus in all others)
  • LH surge makes CL
  • Following ovulation, LH stimulates development of luteal cells from theca and granulosa cells
  • Metestrus (day 2-4)
  • In cow, ovulation occurs here
  • Estrogen levels have decreased, Graafian follicle has ovulated
  • CL is forming, progesterone levels start to increase
  • Embryo partially develops in the oviduct and moves into the uterus (day 4 or 5, depending on the species)
  • Diestrus (Day 5-17)
  • Max corpus luteum size (mature at day 12)
  • High progesterone levels inhibit final follicular development, ovulation and estrus
  • Embryo continues to develop in uterus
  • Embryo signals that its present-no CL regression
  • Not pregnant, PGF2a cause regression, Graafian follicle begins final development and occurs in proestrus for ovulation at estrus!
  • Follicular Phase
  • Proestrus and estrus
  • Luteal Phase
  • Metestrus and diestrus
  • Diffusion of PGF2a from vein to artery, which is wrapped around the vein, carrying PGF2a to CL to regress it
  • Use Luteolysis to do this!
  • In pig, during day 8-12, embryos migrate from horn to horn because has to be at least two embryos in each horn