Anatomy Lecture 2 Unit 1: MALE Reproductive System

Functions of the reproductive system

• Produce gametes (sperm and egg)

• Hormone production

• Structure for fertilization:

  • Deliver sperm cells (males)

  • Receive sperm cells (females)

Female only functions of the reproductive system

• Nurture development of fetus

• Lactation (milk production) for nourishment of baby

Male gonads

• Testes found in the scrotal sac

• Production of sperm through spermatogenesis

• Testosterone

Male Gametes

Spermatozoa (sperm)

Female gonads

Ovaries

Female gametes

Ova (eggs)

Gonadotropin releasing hormone (GnRH)

Hormone released from hypothalamus in males in females

Follicule stimulating hormone (FSH) and Luteinizing hormone

Hormones released from anterior pituitary gland in males and females

Estrogen, progesterone, inhibin

Hormones from the gonads in females

Testosterone, inhibin

Hormones from the gonads in males

Peritoneum

• Landmark/region for both males and females: pelvic floor

• Diamond shape region bordered by:

  • Anterior: Pubic symphysis

  • Posterior: Coccyx

  • Bilateral: Ischial tuberosity

Gameotogenesis

Formation of gametes

Spermatogenesis

Formation of sperm

Oogenesis

Formation of ova

Zygote

Forms haploid (n) cells that fuse to form a single diploid (2n) cell

Autosomes

22 pairs that code for cellular functions

Sex chromosomes

1 pair (23rd pair)

XX chromosomes

Female

XY Chromosomes

Male

Development of male gonads

• Testes form inside the pelvic cavity during fetal development

• Testes descend into scrotum through the inguinal canal out of the superficial inguinal ring

• Lymphatic drainage of the testes is toward area of embryonic sac near the kidneys

Scrotum

• Skin and connective tissue that surround and suspend the testes

• Left testis is slightly below right to prevent compression between the thighs

Median septum

Separates left from right testes

Perineal raphe

Marks the outer boundary of the median septum

Spermatic cord

Palpable within the scrotum and passes through the inguinal canal to enter the pelvic cavity. Formed above each of the testes and surrounds the following

• Ductus (vas) deferens

• Testicular nerve

• Testicular artery

• Testicular veins

• Cremaster muscle

• Fascial layers

Pampiniform plexus

Testicular veins collectively form this network

Scrotal temperature

• Temperature within the scrotum is cooler than the core body temperature as cooler temperatures are needed for spermatogenesis

• 2 to 3 degrees lower than body temperature and the reason why the testes are located on the outside

Factors contributing to scrotal temperature

• Location of scrotum

• Muscles

• Testicular veins

Location of scrotum

Outside of the pelvis (extra pelvis)

Muscles

Contract to bring scrotum towards the body (conditions) and relax to move scrotum farther away from the body (in warm conditions)

• Cremaster (longitudinal): contracts in a cold environment

• Dartos (Layered within sac lining): Contracts in a cold environment and relaxes in a warm environment

Testicular veins

Configured in a “netlike” pattern surrounding the testicular artery

• Acts as a countercurrent heat exchange mechanism between the artery in veins

Three factors that cool the testes

• Location of testes outside the body in scrotal sac

• Involuntary contraction of dartos muscles and cremaster muscles

• Countercurrent heat exchange mechanism between testicular artery and pampiniform venous plexus

Testis anatomy

• Singular: testis

• Have both exocrine and endocrine functions

• Tuna albuginea

• Septa

Tunica albuginea

White connective tissue that surrounds each testis

Septa

• Invaginations of tunica albugenia; walls that form compartments (lobules) within each testis

  • Seminiferous tubules: coiled tubules within each lobule; the specific site of spermatogenesis

Cells of testes

• Germ cells (future sperm)

• Sustenacular cells (sertoli cells)

• Interstitial cells

Germ cells

• Future sperm attached to basement membrane of the seminiferous tubules

• Migrate toward the center of the tubule (lumen) and change shape (divide and differentiate) as they mature toward becoming fully formed sperm

• Undergo meiosis: diploid (2n) to haploid (n)

Sustenacular cells (sertoli cells)

• Form the walls of the seminiferous tubules

• Non dividing

• Respond to FSH by releasing androgen-binding protein (ABP) to stimulate germ cells to migrate toward lumen

• Secrete inhibin: inhibits FSH to help regulate spermatogenesis

• Forms blood-testis barrier via tight junctions between sustentacular cells to protect sperm from being attacked

Interstitial cells (leydig cells)

Fill the interstitial space that surround the seminiferous tubules

• Respond to LH by releasing testosterone

Spermatozoon anatomy of head

Acrosome that contains digestive enzymes and a nucleus containing DNA

Spermatozoon anatomy of mid-piece

Mitochondria which functions to energize sperm (ATP)

Spermatozoon anatomy of tail-piece

Contains flagellum, which functions to move sperm towards the egg

Male tract

Sperm are propelled by the muscular waves of the spermatic tubes during male sexual response

Female tract

The flagella must move in a whip-like fashion to move toward the ovum for fertilization

The way that sperm formed within the seminiferous tubules move

into the rete testis through the efferent ductules and stored in the epididymis

Epididymis

C shaped coiled tube consisting of a head, body and tail

• Sperm are stored and fully matured here and viable for 2-3 months

Phagocytized

The result if sperm are not ejaculated by 2-3 months

Ductus crass deferens

Where sperm moves once ejaculated

Ductus (vas) deferens

• Muscular tube, (not coiled) that is 17inches long

• Ascends from the inferior aspect of epididymis as part of the scrotum into pelvic cavity

• Ends at an enlargement known as an ampulla located near the prostate and seminal vesicles

Vasectomy

When the ductus (vas) deferens is severed in male sterilization

Ejaculatory duct

• Short one inch connector between the ductus (vas) deferens and urethra

• Passes through the posterior aspect of the prostate gland

Urethra

• Passes through the prostate and penis

• A shared pathway by both the reproductive system and the urinary system

• Three portions

Three portions of the urethra

• Prostatic urethra

• Membraneous urethra

• Spongy urethra

Male ejaculate

• Contains sperm (unless male is sterile)

• Sperm suspended in a fluid known as seminal fluid (semen)

• Semen is formed by the accessory glands

Accessory glands

• Form semen

• Seminal vesicles

• Prostate gland

• Bulbourethral (cowper’s) glands

Seminal vesicles

• 2

• Connect ductus deferens to urethra

• 60% of seminal volume

Prostate gland

• 1

• Walnut-sized/shaped, just anterior to rectum making it palpable via rectal exam

• 30% seminal volume

Bulbourethral glands

• 2 pairs of glands at base of prostate; surrounds the membranous urethra

• Secretion serves mainly to lubricate urethra and neutralize its pH (which may be acidic because of urine)

• 10% seminal volume

Semen

• Each ejaculate contains approximately 300 million sperm

• Alkaline pH to neutralize acidic urethra and acidic vagina to increase sperm motility

• Mucous for lubrication

• Fructose as a nutrient substrate for energy production needed for sperm motility

Penis

• Contains root, body, glans

• Prepuce is the foreskin attached that is retractable to expose the glans penis

Smegma

Waxy, oily substance secreted by prepuce and glans

circumcision

Removal of the prepuce

Penis erectile tissues

• Corpus spongiosum

• Corpus cavernosa

Corpus spongiosum

• 1

• Ventral surface

• Spongy tissue that surrounds the urethra

• Engorges to maintain erection and keep urethra open during an erection

Corpus cavernosa

• 2

• Dorsal surface

• Forms most of penile shaft

• Contains spongy erectile tissue that engorge with blood to form and maintain an erection

Puberty

• Hormonal hierarchy; prior to puberty, FSH/LH are nonexistent

• Average age of onset in boys in the U.S is 9-14 years of age, typically completed by 18 but many boys continue to grow taller

Changes in puberty

• Growth of body hair: facial, axillary, abdominal, chest and pubic

• Enlargement of larynx and deepening of voice

• Increased stature, adult males taller than adult females (on average)

• Heavier skull and bone structure

• Broadening of shoulders and chest; shoulders wider than hips

• Increased muscle mass and strength

• Increased secretions of oil and sweat glands, often causing acne and body odor