Male Re. ANAT 2

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Major Functions of the Male Reproductive System

Production, maturation, nourishment and storage of sperm. 2. Transfer of sperm to female body during copulation.

Cremaster Muscle

Raises and lowers testis; low for lower temperature, raised for protection; surrounds spermatic cord.Scrotum Temperature Regulation

Dartos Muscle

Controls surface area of scrotum to regulate temperature.

Spermatic Cord

A connective tissue sheath that contains a network of arteries, veins (pampiniform plexus), nerves, and the ductus (vas) deferens.

Testicular Descent and Gubernaculum

During fetal development, the gubernaculum pulls the testis out of the abdominal cavity through the inguinal canal into the scrotum to reach it by birth.

Tunica Vaginalis vs. Tunica Albuginea

Tunica vaginalis is derived from peritoneum with visceral and parietal layers; Tunica albuginea is a fibrous capsule deep to the visceral layer that divides the testis into 250-300 lobules.

Seminiferous Tubules

Net of tubes where spermatogenesis takes place; contain spermatogenic cells that divide by meiosis to produce sperm.

Interstitial (Leydig) Cells

Cells located between seminiferous tubules that produce and release testosterone.

Efferent Ductules

Structures that carry sperm from the seminiferous tubules and rete testis to the epididymis.

Epididymis

Coiled structure where sperm start to mature and are stored until ejaculation; feeds sperm into the vas deferens.

Ductus (Vas) Deferens

The 'sperm highway' duct that transports sperm from the epididymis through the spermatic cord and into the ejaculatory duct.

Seminal Vesicles

Glands that join the vas deferens to form the ejaculatory duct; they contribute sugar, bicarbonate, and prostaglandins ('packs lunch').

Ejaculatory Duct

Duct that passes through the prostate gland after the seminal vesicles and empties into the prostatic urethra.

Prostate Gland

Doughnut-shaped gland at the base of the bladder surrounding the urethra; contributes sugar and semen liquefier to seminal fluid.

Bulbourethral (Cowper's) Gland

Gland that secretes a lubricating mucus to clean and lubricate the urethra prior to and during ejaculation.

Components of Semen

Mixture containing sperm ($50-100\text{ million}/1\text{\,mL}$), fructose (energy source), fibrinogen (clots semen into a propelled bolus), seminalplasmin (antibacterial enzyme), and prostaglandins (reduce cervical mucus viscosity and trigger uterine reverse peristalsis).

Erectile Tissues of the Penis

One corpus spongiosum (smaller, single erectile tissue surrounding the spongy urethra) and two corpora cavernosa (paired, larger lateral spongy erectile tissues).

Glans Penis and Prepuce

Glans penis is the distal end of the penis containing a high concentration of nerves; prepuce (foreskin) is the skin from the shaft that extends over the glans.

Mechanism of Penile Erection

A reflex mediated by parasympathetic stimulation which releases nitric oxide; this dilates penile arteries, engorges cavernous spaces with blood, and compresses drainage veins.

Mechanism of Ejaculation and Emission

Dependent on sympathetic nerves that stimulate contractions of smooth muscle in the vas deferens, seminal vesicles, and prostate, followed by rhythmic contractions that eject semen from the urethra.

Pathway of Sperm Flow

Seminiferous tubules -> straight tubule -> rete testis -> efferent ductules -> epididymis -> ductus (vas) deferens -> ampulla -> ejaculatory duct -> prostatic urethra -> membranous urethra -> spongy (penile) urethra -> external urethral orifice.

Sperm Anatomy (Head, Midpiece, Tail)

Head: compact, haploid nucleus capped by the acrosome containing enzymes to penetrate the ovum; Midpiece: packed with spiral mitochondria to generate energy; Tail (flagellum): axial filament that whips back and forth for motility.

Mitosis vs. Meiosis Outcomes

Mitosis: one nuclear division yielding two identical diploid ($2n = 46$) somatic cells for growth and repair. Meiosis: two nuclear divisions yielding four genetically distinct haploid ($n = 23$) gametes.

Synapsis and Crossing Over

Occurs during Prophase I of Meiosis I; homologous chromosomes pair closely (synapsis) and break to exchange genetic material at chiasmata, ensuring daughter cells are genetically unique.

Spermatogenesis: Spermatogonia to Primary Spermatocyte

Basally located diploid spermatogonia divide by mitosis; one cell remains a spermatogonium while the other differentiates into a primary spermatocyte ($2n$).

Spermatogenesis: Meiotic Stages

Primary spermatocytes ($2n$) undergo Meiosis I to form haploid secondary spermatocytes ($n$); secondary spermatocytes undergo Meiosis II to yield haploid spermatids ($n$).

Spermiogenesis

The maturation process where spermatids discard most of their cytoplasm and sprout a flagellum to become mature spermatozoa.

Hormonal Stimulation of Spermatogenesis

Hypothalamus secretes GnRH -> stimulates anterior pituitary to produce LH and FSH. LH stimulates Leydig cells to produce testosterone; FSH stimulates Sertoli cells to produce ABP (Androgen Binding Protein). ABP binding to testosterone triggers spermatogenesis.

Hormonal Negative Feedback Loop in Males

Testosterone exerts negative feedback on the hypothalamus to inhibit GnRH production; Inhibin (released by Sertoli cells) acts on the anterior pituitary to selectively inhibit FSH production.

Mitosis Characteristics

• Purpose & Location: Occurs in somatic cells for growth, tissue repair, and replacing lost cells.

• Divisions: Involves one nuclear division.

• Daughter Cells: Results in two diploid ($2n = 46$) daughter cells that are genetically identical to the parent cell.

• Crossing Over: Synapsis and crossing over do not occur.

Meiosis Characteristics

• Purpose & Location: Occurs in germ cells within the gonads (testes and ovaries) to produce gametes (sperm and egg cells) for reproduction.

• Divisions: Involves two nuclear divisions (Meiosis I and Meiosis II).

• Daughter Cells: Results in four haploid ($n = 23$) daughter cells, each genetically unique from the parent cell and from each other.

• Crossing Over: Synapsis and crossing over occur during Prophase I to exchange genetic material.

Mitosis vs. Meiosis: Comparison of Key Differences

• Cell Type: Somatic cells (mitosis) vs. gamete/germ cells (meiosis).

• Divisions: One division (mitosis) vs. two divisions (meiosis).

• Daughter Cell Yield & Ploidy: Two identical diploid ($2n$) cells (mitosis) vs. four unique haploid ($n$) cells (meiosis).

• Synapsis & Crossing Over: Does not occur (mitosis) vs. occurs in Prophase I (meiosis).

The golf-ball sized structure found inferior to the urinary bladder, and surrounding the most proximal portion of the urethra, is called the __________.

prostate gland

The __________ is the site of sperm maturation and storage.

epididymis

The deep region of the penis, surrounding the urethra,that engorges with blood during an erection is known as the ___________.

corpus spongiosum

Which of the following is the correct pathway of sperm cells from their formation to ejaculation?

Seminiferoustubule, rete testis, epididymis, ductus deferens, ejaculatory duct, urethra

By volume, most of the semen is produced in the __________.

seminal vesicles

Which of the following isgenerally accepted as a secondary sex characteristic?

The enlargement of the breasts

When do the testes start secreting testosterone?

In the firsttrimester of fetal development

__________ stimulates the interstitial cells of the testes to secrete __________.

Luteinizing hormone (LH); testosterone

Which hormone suppresses spermatogenesis without affecting testosterone secretion?

Inhibin

The haploid result of meiosis I is called a __________.

secondary spermatocyte

In meiosis, each parent cell produces __________.

four haploid cells

Sperm cells get energy to power their movement from __________, which iscontributed by the __________.

fructose; seminal vesicles