Exam 4 -Male Reproduction

What mechanism in the hypothalamus triggers the increase in testosterone in males at puberty? (p. 730, Fig. 20.9)

?? GnRH from hypothalamus >> luteinizing hormone (LH) and follicle-stimulating hormone (FSH). LH stimulation of the Leydig (interstitial) cells stimulates testosterone secretion. (- feedback) FSH stimulates the Sertoli (sustentacular) cells which in turn stimulate spermatogenesis. Inhibin secreted by the Sertoli cells selectively inhibits FSH secretion.

What is androgen-binding protein? What produces it?

Androgen Binding Protein is used for testosterone transport. Produced/secreted by the sertoli cells in the testes

What is the precursor molecule for steroids (estrogen, testosterone, cortisol, and aldosterone)?

Cholesterol

What are testosterones effects?

Effects before Birth Promoting the development of the male reproductive tract Promote the decent of the testes into the scrotum Effects of Sex-Specific Tissues after Birth Promotes growth and maturation of the reproductive system at puberty Stimulates spermatogenesis Maintains the reproductive tract throughout adulthood Other Reproduction - Related Functions Develops sex drive at puberty (recall DHEA from the adrenal cortex is responsible the development of the female sex drive at puberty). Controls gonadotropin hormone secretion (negative feedback) from the hypothalamus and anterior pituitary. Development of the Secondary Sexual Characteristics Induces male associated hair growth (e.g. beard & chest hair) Causes the deepening to the voice Thick skin Male body configuration Non-reproductive actions Anabolic effects on bone & skeletal muscle Puberty growth spurt Closes the epiphyseal plates after conversion to estrogen by aromatase found mostly in adipose tissue

Ejaculation

Emission emptying of sperm and accessory sex-gland secretions (semen) into the urethra accomplished by sympathetically induced contraction of smooth muscle in walls of ducts and accessory glands

Where are sperm cells stored for maturation and capacitation?

Epididymis and ductus deferens

Know the components of the male sex act. What are the 3 steps?

Erection Ejaculation Expulsion

What are the parts of the sperm? Where does the DNA/mitochondria/enzymes to enable ovum penetration is located?

Head - contains DNA & acrosome (hyaluronidase and proteinase enzymes). Midpiece - contains mitochondria (uses fructose to produce ATP). Tail - a flagellum (containing microtubules)

What is the role of the Y chromosome in sexual development? What factor does it promote? (p. 721, Fig. 20.3)

It determines the gonadal difference under the influence of the Sex-determining Region of the Y chromosome - (SRY) which "masculinizes" the gonads by coding for testis-determining factor (TDF). (In utero, the testes secrete testosterone and Mullerian-inhibiting factor.)

Which cells secrete testosterone? What stimulates its secretion?

Leydig cells which produce testosterone lie in the interstitial tissue between seminiferous tubules in the testis. Secretes due to LH

Mullerian-inhibiting factor.

Mullerian inhibiting factor produced by Sertoli cells in the testes will cause deterioration of the Mullerian (female) reproductive tract.

Mullerian ducts

Mullerian= female reproductive tract.

Secretion from which gland plays a major role in alkalizing semen?

Prostate gland

What type of regulation does testosterone use? What are its effects on phenotype? (Muscles, growth, spermatogenesis, etc.) When is it produced?

Regulated by hypothalamic-pituitary-testicular axis. Testosterone exhibits negative feedback at hypothalamus. LH>>testes>>make testosterone>>testosterone to hypothalamus>> inhibit LH secretion they stop secreting at birth and then start again at puberty

What is the function of the bulbourethral glands? Whats another name for them?

Release lubricating mucus (Cowpers glands)

Testosterone

Secreted in the testes by sertoli cells to induce the development of Wolffian (male) reproductive tract.

What are Sertoli cells? What are their functions?

Sertoli (Sustentacular) cells are support cells embedded among the spermatogenic cells in the seminiferous tubules Sertoli form tight junctions around the testes. Sertoli cells form the "blood-testis barrier" that prevents an immune response against the surface antigens on the spermatogenic cells. Nourish spermatocytes, spermatids, and spermatozoa Mediate the effects of testosterone and follicle stimulating hormone on spermatogenesis Phagocytize excess spermatid cytoplasm as development proceeds Control movements of spermatogenic cells and the release of spermatozoa into the lumen of the seminiferous tubule Secrete fluid for sperm transport and the hormone inhibin Produce and secrete Androgen Binding Protein for testosterone transport.

What is the acrosome of the spermatozoon? What is its function?

The acrosome is the "cap," and it has hyaluronidase and proteinase enzymes. These will help get the sperm into the egg

Y chromosome

The presence of the Y chromosome (SRY) determines the gonadal difference. SRY "masculinizes" the gonads by coding for testis-determining factor (TDF).

Why are the testes located outside of the abdominal cavity?

This is to make sure the sperm dont overheat and can go through spermatogenesis For normal function, the testes need to be several degrees Celsius cooler than normal body (core) temperature (98.6 F).

Wolffian ducts

Wolffian = male reproductive tract.

Understand male sex determination. What 5 things contribute?

Y chromosome Mullerian-inhibiting factor. Wolffian ducts Mullerian ducts Testosterone

Expulsion

forceful expulsion of semen from penis motor neuron induced contraction of skeletal muscles at base of penis

Erection

hardening of the normally flaccid penis to permit its entry into the vagina accomplished by engorgement of penis erectile tissue with blood as a result of marked parasympathetically induced vasodilation of penile arterioles and mechanical compression of veins

What is the prostate gland? What does in secrete?

it surrounds the urethra at the neck of the bladder it secretes an alkaline fluid that neutralizes the acidic vaginal secretions (also triggers the clotting of semen to keep the sperm in the vagina during penis withdrawl- PSA is Used to dissolve the seminal clot)

What is 5-alpha-reductase? What are its actions? (p. 721) What is DHT? What are its functions? (p. 723)

present in small amounts in muscle and converts testosterone to dihydrotestosterone (DHT) DHT is a sex steroid, meaning it is produced in the gonads. fetal development, DHT plays a vital role in the development of the penis and prostate gland During puberty, an increase in the levels of male sex hormones leads to the development of some secondary sex characteristics, such as increased muscle mass, deepening of the voice, development of pubic hair, and a growth spurt. The penis and scrotum grow larger.

After ejaculation, semen will temporarily "clot" at the cervix due to the presence of fibrinogen/fibrin. Which gland is the primary source of this fibrinogen? (p. 731, Table 20.2)

seminal vesicles

What are the functions of the seminal vesicles? What do they do?

supply fructose to nourish the ejaculated sperm secrete prostaglandins that stimulate motility to help transport the sperm within the male/female provide the bulk of the semen (~60%) provide precursors for the clotting of semen. (Fibrinogen)

What substance do sperm consume for energy?

uses fructose to produce ATP