MALE REPRODUCTIVE SYSTEM

Function: Production and delivery of spermatozoa

Primary and Secondary Organs of Male Reproductive System

Primary: Testes: produce sperm and testosterone

Secondary: Sperm transporting ducts: epididymis, ductus deferens (pl. deferentia), ejaculatory ducts and urethra.

Accessory glands: seminal vesicles, prostate gland and bulbourethral (Cowper's) gland.

Penis and Scrotum

Structure & Function of Testes

Housed in scrotum--provides support, protection and keeps testes about 3-4 degrees below body temperature (important for sperm production).

Cryptorchidism (undescended testes): If one or both testicles fail to migrate into scrotom during development, testicle will remain in abdominal cavity or is stuck in the inguinal canal. (crypto = hidden, orchid = testes)

Testes are partitioned in lobules

Each lobule has 1-3 convoluted seminiferous tubules--site of spermatogenesis. Seminiferous tubules consist of Sertoli (nurse) cells that support spermatogonia as they develop, and Leydig (interstitial) cells which produce testosterone.

After sperm mature and leave Sertoli cells, they move to Rete testis and then to the epididymis via the efferent ductules (vas efferens)

Endocrine Function of Testes:
Androgen (testosterone) production by Leydig cells (intersitial cells) --under control of LH secreted by anterior pituitary. Testosterone is necessary for maintenance of spermatogenesis. Maintains secondary sexual characteristics and has anabolic effects (bone & muscle growth, RBC production).

Spermatogenesis
Spermatogonia divide their chromosome number in half via meiosis to become spermatids (46 chromosomes ---> 23 chromosomes). Sertoli cells assist spermatogonia through meiosis and help spermatozoa to mature.


FSH (at puberty) and testosterone are necessary for the transition from spermatids to spermatozoa.
Sperm Structure: Acrosome, head, body and tail.

Ducts and Accessory Structures

Epididymis: efferent ductules feed into epididymis. Storage area.
Ductus (Vas) Deferens: Conveys sperm from epididymis to ejaculatory duct. Muscular layer propels sperm along. Enters abdomen via inguinal canal.
Vasectomy (cutting the vas deferens)

Ejaculatory Duct: formed by ductus deferens (ampulla) and duct from seminal vesicles--enters urethra in prostrate region.

Seminal vesicles: secrete part of semen (fluid for sperm movement)--high in fructose (energy source for sperm) and other nutrients, prostaglandins.
Prostate Gland: Contractile and secretes part of semen, more liquid than seminal vesicle secretion. Helps sperm motility. Basic - neutralizes acidity of vagina.
Bulbourethral (Cowper's) Gland: secretes lubricant prior to ejaculation.
Semen components. Production of Semen Famous Seaman
 
Urethra: prostatic, membranous and penile portions. Common duct for urine and semen.

Penis: External: Shaft, glans penis, prepuce (foreskin)

Circumcision: removal of the prepuce.

Internal: Vascular erectile tissue allows erection:

Corpora cavernosa -- twin vascular chambers. Corpus spongiosum -- surrounds urethra
Sexual Response

Erection: Inhibit SNS, stimulate PNS --> vasoconstriction--> blood accumulation.

Emission: Contraction of muscular elements of ejaculatory ducts and accessory glands--SNS. Semen forced into urethra.

Ejaculation: PNS and SNS--> contraction of bulbospongiosus muscle and muscles of urethra.Impotence: inability to attain or maintain an erection

Viagra: Mechanism of Action

Peyronie's Disease

 

FEMALE REPRODUCTIVE SYSTEM

Function: Production and delivery of ova.

Primary and Secondary Organs

Primary: Ovaries for production of ova, estrogen & progesterone

Secondary : Vagina, oviducts (uterine or fallopian tubes), uterus, & mammary glands.

Accessory structures: Vulva = region containing external genitalia. Consists of labia majora & labia minora, clitoris, clitoral hood and vestibular glands.
 
Ovaries and Ovarian Cycle

Oogenesis -- production of ova by meiosis.

Oogonia become oocytes. Meiosis arrested

Follicles are produced when arrest of meiosis ends. Oogenesis begins during fetal life. A female fetus will develop a few million oocytes before birth, but then they begin to degenerate so by the time a girl enters puberty, she has only 200,000 left. During her lifetime she will ovulate "only" 500 times.

FSH stimulates production of follicles

Associated Structures

Follicles secrete estrogen. Low level of estrogen inhibits FSH/LH production, but when a threshold level of estrogen is achieved, the high level of estrogen stimulates a burst of LH and FSH release. This burst of LH/FSH is the stimulus for ovulation.

Ovulation:
One follicle (on average) will reach maturity and will be expelled from ovary--this is ovulation. Oocyte with its zona pellucida (gel) and corona radiata (circle of cells) are expelled and are then picked up by fimbriae of oviduct (uterine or fallopian tube).

Stimulus for ovulation is a burst of LH and FSH from anterior pituitary.
Follicle remaining in ovary becomes corpus luteum. The corpus luteum secretes progesterone. Progesterone is important for preparing uterine wall for implantation of fertilized egg. Also, part of negative feedback to inhibit gonadotropins and to arrest the ovulation of other follicles.
 
Menstrual Cycle

Constant levels of LH and FSH, plus increasing levels of estrogen from maturing follicle, cause uterine wall (endometrium) to enlarge (proliferative phase).

After ovulation, corpus luteum secretes progesterone and the endometrium becomes thicker and more vascular (secretory or luteal phase).

If pregnancy doesn't occur the corpus luteum is destroyed (becomes the corpus albicans), progesterone secretion decreases, and the endometrial lining dies and is sloughed off -- menstruation or menstrual phase.

Endometriosis

Birth control pills--contain estrogen and progesterone-->inhibit gonadotropin (FSH and LH) secretion--> ovulation doesn't occur. Mimics the luteal/secretory phase.

If egg is fertilized: implanted embryo cells secrete human chorionic gonadotropin (HCG) which acts like LH --> it maintains corpus luteum, thus estrogen and progesterone levels are maintained. Basis of home pregnancy kits -- assay for HCG, replaced "rabbit test". Once placenta is established, corpus luteum is no longer needed.

RU-486: "abortion pill" that blocks progesterone receptors and induces menstruation. Early implanted embryo would be shed with menstrual flow. Prostaglandins given along with RU-486 to generate uterine contractions.

Menopause: End of ovarian & menstrual cycles.