Ch 27 - Reproductive System

Testes

Sperm producing paired male gonads within the scrotum

Sperm is delivered to body through which ducts?

Epididymis → ductus vans deferens → ejaculatory duct → urethra

Accessory sex glands

Seminal glands, prostate, bulbo-urethral glands

Scrotum

Sac of loose skin containing testes

Tunica vaginalis

Partially covers testes

Tunica albuginea

Underneath tunica vaginalis, connective tissue capsule that forms septa creating compartments

Seminiferous tubules

Tube-like structures in testicles where sperm is produced (spermatogenesis) and carries sperm out of testes

Spermatogonia

Diploid stem cells that begin spermatogenesis

Cells of spermatogenesis in order

Spermatogonium (2n) → primary spermatocyte (2n) → secondary spermatocyte (n)→ spermatid → sperm cell

Which cells go through meiosis I and II

Primary spermatocytes go through meiosis I → forming secondary spermatocytes (haploids)

Secondary spermatocytes go through meiosis II → four spermatids

Purpose of sperm

To reach secondary oocyte → fertilization → zygote

Head of nucleus

Contains nucleus w/ 23 chromosomes

Acrosome

Covers head, contains enzymes to aid fertilization

Neck of sperm

Contains centrioles forming microtubules that make up rest of tail

Middle piece of sperm

Contains mitochondria → ATP → energy for locomotion

Principal piece + end piece

Make up tail for locomotion

What does gonadotropin releasing hormone (GnRH) do at puberty?

Stimulates cells in anterior pituitary gland to produce LH and FSH

In male reproduction - what does LH target?

LH targets Leydig cells in testes to produce testosterone

In male reproduction - what does FSH do?

Stimulates spermatogenesis (S = S) targets Sertoli/sustentacular cells to promote ABP production

Function of ABP

Allows testosterone to bind for spermatogenesis

Function of testosterone and dihydrotestosterone

• development of reproductive organs

• secondary sex characteristics

• spermatogenesis

• anabolism of protein in bones and muscles

controlled by negative feedback

Sperm flow in testes

Seminiferous tubules → straight tubules → rete testis → efferent ducts → epididymis

What happens in the epididymis?

Sperm matures and degenerated sperm is reabsorbed

Seminal vesicles

Secrete alkaline substance w/ fructose, prostaglandins, clotting protein

Prostate

Secretes acidic fluid (citric acid, proteolytic enzymes, acid phosphatase, seminalplasmin)

Bulbourethral (Cowper’s) glands

Secrete alkaline fluid during sexual arousal to neutralize acids from urine and mucus for lubrication

Semen definition, avg ejaculate, how many sperm per mL

Sperm and seminal fluid

2.5-5mL, 50-150 mil sperm/mL

pH 7.2-7.7

2 corpora cavernosa, 1 corpus spongiosum

The three cylindrical masses of the penis

Ovaries

Paired female gonads

• produce female gametes (ova)

• secrete estrogen, progesterone, inhibin, relaxin

Germinal epithelium

• outer ovarian surface

Tunica albuginea

connective tissue capsule below germinal epithelium

Ovarian cortex

• below tunica albuginea

• contains follicles, stromal cells

Ovarian medulla

• connective tissue, blood vessels, lymphatic vessels, nerves

What do the ovarian follicles contain?

• oocytes in different developmental stages

• follicular cells

• granulosa cells

Graafian follicle

Mature follicle, contains secondary oocyte

Uterine/fallopian tube

• pathway for sperm to reach ova (site of fertilization)

Endometrium: Stratum functionalis

Shed each month during menstruation

Endometrium: stratum basalis

Permanent, gives rise to new stratum functionalis after each menstruation

Four phases of female reproductive cycle

1. menstrual

2. preovulatory

3. ovulation

4. postovulatory

What occurs in the preovulatory stage?

In ovaries: follicles grow under FSH

In uterus: endometrium thickens due to estrogen

What occurs during ovulation?

Surge in LH = release of secondary oocyte from ovary

What happens postovulatory?

Corpus luteum forms, secretes progesterone and some estrogen

• thickens endometrium more

• if fertilization doesn’t occur, corpus luteum degenerates and progesterone lvl declines

What does low estrogen and progesterone stimulate?

Secretion of FSH

What happens to estrogen as follicles develop?

Estrogen rises gradually, peaking before ovulation triggers LH surge

After ovulation, in luteal phase

Progesterone is high from corpus luteum, estrogen is moderate, FSH and LH are suppressed

What effect does estrogen have on LH and GnRH

Positive feedback effect, LH surge causes ovulation