CH 28 Concise

The male reproductive system consists of the gonads (testes), ducts, accessory glands, and external genitalia.
Testes produce androgens (primarily testosterone) and approximately $0.5 \times 10^9$ sperm per day.
The scrotum maintains sperm development at a temperature approximately $1.1^\circ\text{C}$ lower than body temperature; the skeletal cremaster and smooth dartos muscles adjust testicular position for temperature regulation.
The pathway of sperm production involves the seminiferous tubules (totaling half a mile in length) $\rightarrow$ straight tubules $\rightarrow$ rete testis $\rightarrow$ efferent ductules (ciliated) $\rightarrow$ epididymis $\rightarrow$ ductus deferens (vas deferens) $\rightarrow$ urethra.
The epididymis stores and protects sperm for up to 3 weeks, facilitates maturation, and recycles damaged sperm.
The ductus deferens can store sperm for several months in its ampulla and uses peristaltic contractions for transport.

Interstitial endocrine cells (Leydig cells) produce androgens such as testosterone and androsterone.
Nurse cells (Sertoli cells) maintain the blood-testis barrier, provide nutrients, and secrete inhibin, which provides negative feedback to the hypothalamus (GnRH) and pituitary gland (FSH).
Luteinizing hormone (LH) stimulates Leydig cells to produce testosterone; Follicle-Stimulating Hormone (FSH) and testosterone stimulate nurse cells to produce androgen-binding protein (ABP).
Testosterone maintains libido, stimulates growth, and sustains secondary sex characteristics and accessory organs.
Spermiogenesis is the specific phase where immature spermatids differentiate into mature, mobile sperm.
Capacitation is the process where sperm becomes fully motile, occurring when they mix with seminal gland secretions.

Seminal glands (seminal vesicles) contribute $60\%$ of semen volume; secretions include fructose for metabolism, prostaglandins for muscle contraction, and fibrinogen for temporary clotting.
The prostate gland contributes $\frac{1}{4}$ of semen volume; it contains prostatic fluid with acid phosphatase and amylase to prevent sperm coagulation.
Bulbo-urethral glands (Cowper’s glands) secrete alkaline mucus to neutralize urinary acids in the urethra.
Semen consists of seminal fluid and a sperm concentration of $20\text{--}100 \times 10^6 \text{ sperm/mL}$ .
Enzymes in semen include protease (to dissolve vaginal mucus), seminalplasmin (antibiotic), and fibrinolysin (to liquefy clotted semen).

Ovaries produce oocytes and secrete estrogens, progesterone, and inhibin.
The uterine tubes (fallopian tubes) use ciliary movement and peristalsis to move oocytes toward the uterus; fertilization typically occurs between the ampulla and isthmus.
Peg cells in the uterine tube provide nutrients for sperm and the pre-embryo.
The uterus contains three layers: the perimetrium (outer), myometrium (middle muscular), and endometrium (inner glandular).
The vaginal environment is kept acidic by harmless bacteria to restrict pathogen growth.
Oogenesis begins before birth; oogonia (stem cells) produce primary oocytes ( $2 \times 10^6$ at birth, reduced to $400,000$ by puberty via atresia).
Meiosis I produces one secondary oocyte and nonfunctional polar bodies; meiosis II only completes if fertilization occurs.

The Ovarian Cycle (28 days) includes the Follicular phase (day 1–14; stimulated by FSH), Ovulation (day 14; triggered by an LH surge), and the Luteal phase (day 14–28; corpus luteum formation).
The corpus luteum secretes progesterone to maintain the uterine lining; if no fertilization occurs, it becomes the corpus albicans.
The Menstrual Cycle includes:
- Menstrual phase (days 1–7): Shedding of the functional layer of the endometrium and $30\text{--}50\,\text{mL}$ blood loss.
- Proliferative phase (days 7–14): Estrogen-driven restoration of the functional layer.
- Secretory phase (days 14–28): Progesterone and estrogen drive uterine gland enlargement and increased vascularization.
Basal body temperature fluctuates during the cycle, typically rising from $36.2^\circ\text{C}$ to $36.5^\circ\text{C}$ during the luteal phase.

Prostate cancer is detected via a Prostate-Specific Antigen (PSA) blood test; Benign Prostatic Hyperplasia (BPH) is treated by Transurethral Resection of the Prostate (TURP).
The penis contains three cylindrical erectile tissues: two corpora cavernosa and one corpus spongiosum.
Circumcision is the removal of the prepuce (foreskin), which can lower risks of UTI, HIV, and penile cancer.
Cervical cancer is detected via a Pap smear (exfoliative cytology).
Breast cancer is a leading cause of death in women; the mammary glands produce milk (lactation) via lobules and lactiferous ducts.

Why will the cremaster muscle be relaxed on a warm day? Because normal sperm development depends on the testes being $1.1^\circ\text{C}$ cooler than body temperature.
What is NOT a function of nurse cells? Producing androgens like testosterone; this is the role of Leydig (interstitial endocrine) cells.
What occurs during spermiogenesis? Spermatids differentiate into mature sperm.
What is a direct effect of low FSH secretion in males? The rate of sperm production decreases.
Which layer of the uterus is sloughed off during menstruation? The functional layer of the endometrium.
What happens to the corpus luteum if fertilization does not occur? It disintegrates into a corpus albicans.
Why does oogenesis yield only one functional ovum? It produces two or three nonfunctional polar bodies that disintegrate, and cytoplasm is distributed unevenly.
What happens if the LH surge does not occur? Completion of meiosis I by the primary oocyte and ovulation will not occur.