WileyPlus Tortura Principles of A&P 14 ed Chp. 28.1

FUNCTIONS OF THE MALE REPRODUCTIVE SYSTEM

1. The testes produce sperm and the male sex hormone testosterone. 2. The ducts transport, store, and assist in maturation of sperm. 3. The accessory sex glands secrete most of the liquid portion of semen. 4. The penis contains the urethra, a passageway for ejaculation of semen and excretion of urine.

haploid cells (n) have

23 chromosomes.

Diploid cells (2n) have

46 chromosomes

spermatogenesis takes

65-75 days

Blood-testis barrier

A barrier formed by Sertoli cells that prevents an immune response against antigens produced by spermatogenic cells by isolating the cells from the blood.

Tunica albuginea

A dense white fibrous capsule covering a testis, the penis, or deep to the surface of an ovary.

follicle-stimulating hormone (FSH)

A hormone released by the pituitary gland that stimulates the production of sperm in the male and growth of the follicle (which produces the egg) in the female.

Inhibin

A hormone secreted by the gonads that inhibits release of follicle-stimulating hormone (FSH) by the anterior pituitary.

Acrosome

A lysosome like organelle in the head of a sperm cell containing enzymes that facilitate the penetration of a sperm cell into a secondary oocyte

Sperm cell

A mature male gamete. Also termed spermatozoon; once formed, it is released into the lumen of the seminiferous tubule

Nucleus

A spherical or oval organelle of a cell that contains the hereditary factors of the cell, called genes. A cluster of unmyelinated nerve cell bodies in the central nervous system. The central part of an atom made up of protons and neutrons.

Interstitial cell

A type of cell that secretes testosterone; located in the connective tissue between seminiferous tubules in a mature testis. Also known as a Leydig cell.

Sperm

About 300 million sperm mature each day. complete the process of spermatogenesis. A sperm is about 60 μm long and contains several structures that are highly adapted for reaching and penetrating a secondary oocyte

dihydrotestosterone (DHT)

An androgen secreted by the testes that differentiates pareurethral glands into prostate and Cowper's gland. In the prostate and seminal vesicles, 5 alpha-reductase converts testosterone to a more potent androgen called

Stimulation of anabolism.

Androgens are anabolic hormones; that is, they stimulate protein synthesis. This effect is obvious in the heavier muscle and bone mass of most men as compared to women.

Development of sexual function.

Androgens contribute to male sexual behavior and spermatogenesis and to sex drive (libido) in both males and females. Recall that the adrenal cortex is the main source of androgens in females.

Development of male sexual characteristics.

At puberty, testosterone and dihydrotestosterone bring about development and enlargement of the male sex organs and the development of masculine secondary sexual characteristics.

spermiation

At the end of spermatogenesis, spermatids undergo their final maturation and are released during a process called _____ from the supporting Sertoli cells into the lumen of the seminiferous tubule.

Prenatal development.

Before birth, testosterone stimulates the male pattern of development of reproductive system ducts and the descent of the testes. Dihydrotestosterone stimulates development of the external genitals

Primordial germ cells

Cells that arise from the yolk sac endoderm and enter the testes during the fifth week of development.

Release of FSH is stimulated by

GnRH and inhibited by inhibin

release of LH is stimulated by

GnRH and inhibited by testosterone.

Androgens

Masculinizing sex hormones produced by the testes in males and the adrenal cortex in both sexes; responsible for libido (sexual desire); the two main androgens are testosterone and dihydrotestosterone.

Dartos muscle

Muscle tissue composed of bundles of smooth muscle fibers that makes up the scrotal septum.

Which cells secrete inhibin?

Sustentacular cells secrete inhibin.

Which hormones inhibit secretion of FSH and LH by the anterior pituitary?

Testosterone inhibits secretion of LH, and inhibin inhibits secretion of FSH.

Cryptorchidism

The condition of undescended testes.

Which muscles help regulate the temperature of the testes?

The cremaster and dartos muscles help regulate the temperature of the testes.

Spermatogenesis

The formation and development of sperm in the seminiferous tubules of the testes

spermatids

The four haploid cells resulting from meiosis II

Which cells secrete testosterone?

The interstitial (Leydig) cells of the testes secrete testosterone.

Spermiogenesis

The maturation of spermatids into sperm.

What are the functions of each part of a sperm cell?

The sperm head contains the nucleus with 23 highly condensed chromosomes and an acrosome that contains enzymes for penetration of a secondary oocyte; the neck contains centrioles that produce microtubules for the rest of the tail; the midpiece contains mitochondria for ATP production for locomotion and metabolism; the principal and end pieces of the tail provide motility.

What tissue layers cover and protect the testes?

The tunica vaginalis and tunica albuginea are tissue layers that cover and protect the testes.

secondary spermatocytes

The two cells formed by meiosis I; Each secondary spermatocyte has 23 chromosomes, the haploid number (n). Each chromosome within a secondary spermatocyte, however, is made up of two chromatids (two copies of the DNA) still attached by a centromere. No replication of DNA occurs in the secondary spermatocytes.)

Secondary sex characteristics are traits that distinguish males and females but do not have a direct role in reproduction.

These include muscular and skeletal growth that results in wide shoulders and narrow hips; facial and chest hair (within hereditary limits) and more hair on other parts of the body; thickening of the skin; increased sebaceous (oil) gland secretion; and enlargement of the larynx and consequent deepening of the voice.

Sustentacular cells support and protect developing spermatogenic cells in several ways

They nourish spermatocytes, spermatids, and sperm; phagocytize excess spermatid cytoplasm as development proceeds; and control movements of spermatogenic cells and the release of sperm into the lumen of the seminiferous tubule. They also produce fluid for sperm transport, secrete the hormone inhibin, and regulate the effects of testosterone and FSH (follicle-stimulating hormone).

spermatogonia

begins spermatogenesis, type of stem cell; contain the diploid (2n) number of chromosomes. differentiate into primary spermatocytes

Testosterone and dihydrotestosterone both

bind to the same androgen receptors, which are found within the nuclei of target cells.

Testosterone also is

converted in the brain to estrogens (feminizing hormones), which may play a role in the development of certain regions of the brain in males.

tunica vaginalis

derived from the peritoneum and forms during the descent of the testes, partially covers the testes

development of testes

develop near the kidneys, in the posterior portion of the abdomen, and they usually begin their descent into the scrotum through the inguinal canals (passageways in the lower anterior abdominal wall; see Figure 28.2) during the latter half of the seventh month of fetal development.

raphe (RĀ-fē = seam)

external median ridge of the scrotum

hydrocele

fluid in the tunica vaginalis

The hormone-receptor complex regulates

gene expression, turning some genes on and others off. Because of these changes, the androgens produce several effects

In meiosis I,

homologous pairs of chromosomes line up at the metaphase plate, and crossing-over occurs. Then, the meiotic spindle pulls one (duplicated) chromosome of each pair to an opposite pole of the dividing cell.

When testosterone concentration in the blood increases to a certain level, it

inhibits the release of GnRH by cells in the hypothalamus.

scrotal septum

internal, divides the scrotum into two sacs, each containing a single testis

LH stimulates

interstitial cells,

lowered temperature is maintained within the scrotum because

it is outside the pelvic cavity

ABP binds to testosterone,

keeping its concentration high

Primary spermatocytes

like spermatogonia, are diploid (2n); that is, they have 46 chromosomes.

testes (TES-tēz = witness), or testicles

male gonads, produce haploid sperm. paired oval glands in the scrotum measuring about 5 cm (2 in.) long and 2.5 cm (1 in.) in diameter (mass 10-15 grams)

Reproductive organs are adapted for

producing new individuals and passing on genetic material from one generation to the next.

negative feedback system

regulates testosterone production; control of blood level of testosterone.

luteinizing hormone (LH)

secreted by the anterior lobe of the pituitary gland, stimulates ovulation in females and testosterone secretion in males

spermatogenic cells

sperm forming cells in seminiferous tubules

spermatogonia

sperm stem cells

spermatogenic cells from least mature to most mature

spermatogenic cells, sustentacular cells, spermatogonia, primary spermatocyte, secondary spermatocyte, (primordial germ cells) spermatid, sperm cell (spermatozoom)

FSH acts indirectly to

stimulate spermatogenesis

Sustentacular cell

supporting cell in the seminiferous tubules that secretes fluid for supplying nutrients to sperm and the hormone inhibin, removes excess cytoplasm from spermatogenic cells, and mediates the effects of FSH and testosterone on spermatogenesis. Also called a Sertoli cell.

In response to stimulation by FSH and testosterone,

sustentacular cells secrete androgen-binding protein (ABP). Dashed red lines indicate negative feedback inhibition.

FSH and testosterone act synergistically on the

sustentacular cells to stimulate secretion of androgen-binding protein (ABP) into the lumen of the seminiferous tubules and into the interstitial fluid around the spermatogenic cells

In meiosis II,

the chromosomes line up in single file along the metaphase plate, and the two chromatids of each chromosome separate.

In response to cold temperatures,

the cremaster and dartos muscles contract. reduces heat loss

Testosterone stimulates

the final steps of spermatogenesis in the seminiferous tubules.

Spermiogenesis involves

the maturation of spermatids into sperm.

What is the outcome of meiosis I?

the number of chromosomes in each cell is reduced by half.

scrotum

the supporting structure for the testes, consists of loose skin and underlying subcutaneous layer that hangs from the root (attached portion) of the penis

The location of the scrotum and the contraction of its muscle fibers regulate

the temperature of the testes.

Contraction of the cremaster muscles moves the testes closer to the body,

where they can absorb body heat. (hot temperatures do the reverse)

cremaster muscle

a series of small bands of skeletal muscle that descend as an extension of the internal oblique muscle through the spermatic cord to surround the testes.

Normal sperm production requires a temperature

about 2-3°C below core body temperature

each primary spermatocyte replicates its DNA

and then meiosis begins

Hormonal Control of Testicular Function

at puberty certain hypothalamic neurosecretory cells increase their secretion of gonadotropin-releasing hormone (GnRH)