seminiferous tubules

• sweat glands
• contraction and relaxation of muscles (cremaster and tunica dartos)
• pampiniform plexus: countercurrent exchange

1. spermatocytogenesis: mitosis of spermatogonia

2. meiosis: results in haploid germ cells (round spermatids)

3. spermiogenesis: differentiation / metamorphosis of round spermatids to spermatozoa

• sustentacular or nurse cells: contact all stages of spermatogenesis
• secrete estrogens, inhibin, activin, GnRH like peptide, proteins, lactate, pyruvate, tubule fluid
• tight junctions form blood-testis barrier (along with myoid cells): prevent escape of sperm/ control environment to be specific for sperm

1. male germ cells are replenished while female decrease during life

2. males continue mitosis while females stop soon after birth (preset number of formed germ cells)

1. chromosome number reduces from diploid to haploid

2. crossing over (chiasma/formation of tetrads) results in more genetic diversity among gametes

pachytene (part of prophase)

damage by high testicular temp or inappropriate gonadotrophin levels

contain half of chromosomal complement

undergo second meiosis: duplicated chromosomes each go into one daughter cell

acrosome forms

flagellum forms

cytoplasmic volume decreases

gradual release of spermatozoa into lumen of seminiferous tubules

still has residual body (cytoplasmic droplet) - removed by sertoli cells in the lumen

1. E Elongation (postrelase)

2. G Group formation (premeiotic)

3. M Maturation (postmeiotic)

4. R Prerelease

EGMR: least to most advanced component cell associations

30-60 days depending on location of damage

represents interval between sensitive preleptotene stage and ejaculation

describes sperm development by spatial arrangement

from rete outward: RMGE

site of reversal in seminiferous tubule

EGMR

reach rete again: RMGE

triggers Testosterone production from Leydig cells

from leydig cells

essential for development and maintenance of spermatogenesis, other male characteristics

from sertoli cells in response to FSH stimulation

inhibits anterior pituitary to reduce FSH

negative feedback loop

from sertoli cells

stimulates anterior pituitary to stimulate FSH production

from sertoli cells

triggers spermatocytogenesis via androgens, moves testosterone to blood vessels and lymph for distribution to rest of body

from sertoli cells

important spermatogenic cell intracellular reductant and detoxicant

• result of testosterone conversion by sertoli cells
• present in adluminal and basal conpartment of seminiferous tubules and in bloodstream
• synergistic effect w testosterone: negative feedback
• can be measured to determine presense of cryptorchid in males without outer testicles (eg. determine gelding or cryptorchid)

converted form of testosterone in sertoli cells

greater biological potency than T

• result of testosterone concentrations
• anabolic or nitrogen retention effect involving increase in muscle mass
• also results in deeper voice from thicker vocal cord muscles

increase in photoperiod brings on increased spermatogenic and endocrine functions of gonads

ex: stallion

decrease in photoperiod brings on increase in testicular function

ex: sheep and goats

• hypothalamus and pineal gland are involved
• inc GnRH and LH
• leydig cells respond to pattern of LH release, not amount
• smaller amplitude but longer duration of LH: release large amounts of testosterone
• FSH increase but circulating levels decrease once activation is complete

secreted as salivary pheromones

also contribute to boar taint meat

lip curls up to block nostrils, breathe in through mouth

vomeronasal organ used to detect less volatile pheromones in female

sympathetic

follows emission, forces spermatozoa and secretions into urethra

glans penis -> internal pudendal -> spinal cord reflex arc

parasympathetic

hypogastric plexus -> urethralis, ischocavernosus and bulbospongiosus muscles

sigmoid flexure straightens w relaxation of retractor penis muscle

still have vascular component of erection

increase in penile diameter limited by CT (show-ers nor grow-ers?)

ex: bulls, boars and rams

relaxation of retractor penis muscle and penile engorgement result in significant increase in diameter and length of penis

(grow-ers not show-ers?)

ex: stallion

• vasodilaton of ateries mediated by nitric oxide
• intermittent contractons of ischiocavernosus muscles
• compression of penile veins
• blood trapped in cavernosus sinuses

entry of penis into vagina

marks initiation of coitus

combination of spermatozoa and seminal plasma

product of ejaculation

posterior pituitary

effects contraction of epidydimal smooth muscle

forces more sperm cells into the male duct system for ejaculation

maintain spermatozoa in a quiescent state with little oxidizable substrates and high concentration of potassium

in tail of epidydimus: cells become capable of motility from forward motility protein located there

ampulla

seminal vesicles

prostate

bulbourethral

disseminate: surround urethra without penetrating voluntary muscle

discrete: form definite body around urethra

concentrates zinc; secretes fructose, citric acid, cholesterol, proteins, amino acids, enzymes

spermine: human only

enlargements of distal ends of ductus deferens

most prominent in dog and stallion

stallion: produce some inositol, ergothioneine

secrete fructose,inositol, ergothioneine, citric acid, amino acids, proteins, potassium, lipid, phosphorylcholine, prostaglandins

absent in dog

located near the bulb of the penis

prepare urethra for ejaculation

erect penis creates pressure, squeezing glands

secretions rinse urine from the urethra and raise pH

absent in the dog

electrolytes, fructose, ascorbic acid, enzymes, vitamins, hormones, growth factors

more important in species with vaginal depositon of sperm as opposed to cervical or uterine

in female reproductive tract

renders sperm cell capable of fertilizing an egg

removal and/or alteration of seminal plasma protein components that stabilize membranes of sperm cells

necessary for sperm to interact with egg

release of egg penetrating enzymes

motility: at least 70% motile

morphology: should 70% or more normal

sperm concentration

abnormalities acquired during development in the testis

important for fertility: should be less than 20% primary defects

onset of lactation, CL functioning

negative control by dopamine

increased by increased photoperiod, suckling and nursing, estrogens

estradiol: from growing follicle

progesterone: from corpus luteum

stimulates follicle growth (not initial development)

directs granulosa cells to convert androgens to estrogens (aromatase enzymes)

final maturation of follicle and ovulation

supports CL formation

directs androgen synthesis by thecal cells

first estrus with ovulation, followed by normal CL formation and function

mechanism controlled by hypothalamus and GnRH

undergo multiple estrous cyles in a limited time of year

ex: sheep, goats, horses

cycle throughout the year

ex: cow, sow

require copulation to ovulate

ex cat, rabbit, llama, camel

from ovary

induces estrus

stimulates GnRH secretion and increases pituitary sensitivity to GnRH

positive feedback effect causes LH surge and smaller FSH surge

period of sexual receptivity

ovulation occurs during or shortly after estrus

period for establishing CL activity

interval between estrogen and progesterone dominance of the cycle

when CL has become functional

progesterone concentrations increase

longest phase of cycle (cow)

luteolysis

decrease in progesterone

rapid follicle growth

all species: accept mounting by male

cows: stand to be mounted by females (that may or may not also be in estrus)

ewes: seek male

mare: breeding stance and winking of clitoris

gilt or sow: rigid with ears erect, can sit on its back

queen: vocalising! and lordosis, treading

bitch: sanguineous secretions due to estrogens

pheromones

tactile stimulation

presense of a male

no limit to sexual receptivity

start cycle at first day of menstruation

prominent sloughing of endometrial lining due to loss of gonadal steroids

follicular growth dominates the cycle (not luteal phase)

estradiol stimulates endometrial proliferation

ovulation occurs mid-cycle

menstrual cycle

follicular phase

encreased estradiol causes endometrial proliferation

menstrual cycle

luteal phase

endometrial glands secrete fluid into the uterine lumen

at birth: oogonia (germ cells) undergo meiotic division to become oocytes

oocytes stay in resting phase until puberty

meiosis is resumed in a few cells during each estrous cycle

oogenesis occurs simultaneously with follicular growth

oocyte surrounded by granulosa cells and thecal cells with basement membrane in between

formed by granulosa cells in early follicular growth

mucopolysaccharide membrane surrounding oocyte

secondary follicle

follicle does not undergo ovulation so it regresses

loss of antrum (fluid cavity), shrinking of nuclei

almost all follicles become atretic

viable follicles have high estradiol concentration in follicular fluid while atretic follicles have elevated androgens

groups of follicles initiate growth

first wave occurs after gonadotropin surge before ovulation

one follicle becomes primary while others regress

sheep, cattle and horses have waves during luteal phase

pig, rat and human only during follicular phase

waves also occur during pregnancy and before puberty

biosynthesis of follicular estradiol

LH directs androgen synthesis in thecal cells

FSH directs androgen conversion to estrogens in granulosa cells

first division normally complete prior to ovulation 

second division completed at time of fertilization

prior to first meiosis

in bitch, primary oocyte is ovulated

increase in PGE and F

formation of multivesicular bodies: proteolytic enzymes digest ground substance to allow escape of oocyte

originate from theca

responsive to LH

originate from the granulosa

not responsive to LH

secrete majority of basal progesterone

cow: LH, hCG, GnRH

rat: prolactin

canine: LH and prolactin

rabbit and pig: estrogen

cat, horse

melatonin determines breeding season

sudden increase in feed intake to stimulate ovulation rate

in pigs and sheep