Reproduction and survival the 2 components of evolutionary fitness.
Male Reproductive System
Anatomy
Primary organs paired testes (testicles)
Contained in scrotum, which is divided sagitally by septum
Suspended outside pelvic cavity to maintain 3-degree lower temperature for sperm
Scrotum has lots of melanin -- UV protection in some species
2 layers of muscle help control degree of suspension of scrotum
Testis is surrounded by 2 tunics
Lobules contain 1 to 4 seminiferous tubules, where sperm are produced
Seminiferous tubules in a lobule join to form tubulus rectus, which carries sperm into the rete testis, a reticular network of tubules. From there, efferent ductules carry sperm out of the testis into the epididymis, which is a comma-shaped structure lying superior and posterolateral to the testis.
Duct system carries sperm from testis to outside body. Composed of:
Accessory glands
Externally made up of shaft, glans penis, prepuce. Internally, corpus spongiosum (forms glans and bulb) and 2 dorsal corpora cavernosa which are essential to erection and proximally form crura. Both types of corpora are erectile tissue, which contains spongy connective tissue with lots of vascular spaces, as well as smooth bulbospongiosum muscles.
Semen
Composed of sperm + secretions of accessory glands.
Fructose from seminal vesicles nourishes sperm.
Prostoglandins may break down mucus at cervix.
Enzymes enhance motility of sperm.
2 - 6 ml ejaculate, 50 - 100 million sperm/ml
Formation of sperm in seminiferous tubules from cells (spermatagonia) lining tubules. These divide continuously mitotically until puberty. At puberty, both A & B cells are produced. A continues as before, B becomes a primary spermatocyte. These undergo meiosis I and II to form 4 haploid spermatids each.
Spermiogenesis
transformation of spermatid to sperm
Sperm has head (genetic) with acrosome, midpiece (metabolic) containing mitochondria, and tail (locomotor) which is a flagellum
Sustentacular cells form basal and adluminal compartments in seminiferous tubules. These cells are tightly joined to form blood-testis barrier to prevent antigenic reactions to sperm's proteins--possible basis for male contraceptive.
Whole process of sperm formation takes 64-72 days.
Male sexual response
two parts:
Hormonal regulation
Brain-testicular axis--hypothalamus to pituitary to testes. Series of hormones culminating in testosterone production. Testosterone responsible for secondary male sexual characteristics. See table
Female reproductive system
Anatomy
Primary sex organs are ovaries. These produce ova (eggs), estrogens, progesterone.
Most of female repro system consists of internal genitalia, unlike males, which are primarily external.
Ovarian ligament attaches ovary to uterus.
Suspensory ligament connects ovary to body wall.
Mesovarium suspends ovary, between other 2 ligaments, with susp. lig. helps make up broad ligament
Ovarian arteries reach ovary through susp. lig.
Ovary covered with tunica albuginea and germinal epithelium
Internally, poorly separated cortex and medulla
Uterine (fallopian tubes, oviducts) tubes--ca. 10cm. Oocytes released into peritoneal cavity. Picked up by fimbriae on infundibulum of ampulla of uterine tube. Tubes have layers of circular and longitudinal muscle, as well as ciliated cells. Mesosalpinx, part of broad ligament, supports tube. Tiny internal diam. in places.
Uterus--size and shape of inverted pear in nulliparous females. Main parts are fundus, body, isthmus, cervix, lumen. Anteverted in young, retroverted with age. 3 layers in wall:
Vascular supply to uterus consists of uterine arteries that divide into arcuate arteries which are primarily in the myometrium. These send radial branches into endometrium. These branches form straight arteries which supply the stratum basalis, and spiral arteries which supply the stratum functionalis and break down when layer sheds.
Uterus is supported laterally by mesometrium (part of broad ligament), inferior to this by lateral cervical (cardinal) ligaments. Posteriorly, paired uterosacral ligaments support the uterus, while round ligaments support it anteriorly.
Vagina extends from cervix to exterior. Moistened from cervical or vestibular glands.
Glycogen stored in epithelium of vagina is metabolized to lactic acid by bacteria, resulting in pH of 3.5-4.0
External genitalia consist of mons pubis, labia majora (homologous to scrotum), labia minora
Labia minora enclose vestibule containing urethral orifice, vaginal orifice, greater vestibular glands (aka Bartholin's glands--homologous to bulbourethral glands) and the erectile clitoris, which is homologous to glans penis. Note definition of homolog.
Mammary glands --present in both, only functional in females. Modified sweat glands. Areola contains sebaceous glands. Mammary gland consists of 15-25 lobes radiating from nipple. Also, fat, fibrous connective tissue, and suspensory ligaments are found in the breasts. Within the lobes are lobules containing alveoli into which the milk is secreted. Lactiferous ducts open to outside of nipple. Ducts have an enlarge sinus to store milk. All parts of glands reduced except in last trimester of pregnancy or while nursing.
Physiology
Sequence of oogenesis (ovarian cycle)
Estrogen analagous to testosterone, progesterone more regulatory
Uterine or menstrual cycle--responses of endometrium to ovarian hormones
Female sexual response primarily nervous. Generally tactilely stimulated. Not directly associated with reproduction as in males.
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