Chapter 19 - Reproductive Systems

The second meiotic division (meiosis II)

each of the secondary spermatocytes begins with one member of each homologous pair (haploid) separates the chromatids, producing cells that are still haploid, but whose chromosomes are no longer in the replicated (two chromatids) form.

primordial follicle

follicle consists of a single, large cell, called a primary oocyte, surrounded by epithelial cells called follicular cells.

for the primary spermatocyte that undergoes meiosis...

four sperm cells form, with 23 chromosomes each.

spermatogenic cells (germ cells)

give rise to sperm cells

midpiece of a sperm cell

has a central, filamentous core and many mitochondria organized in a spiral.

body, or shaft, of the penis

has three columns of erectile tissue — a pair of dorsally located corpora cavernosa — a single, ventral corpus spongiosum A tough capsule of dense connective tissue surrounds each column. Skin, a thin layer of subcutaneous tissue, and a layer of connective tissue enclose the penis.

rhythmic peristaltic contractions

help move sperm cells through the epididymis as they do this, the cells mature

inhibin

hormone that inhibits the anterior pituitary gland by negative feedback. This action prevents oversecretion of FSH.

The ___________________ regulates testosterone output through ___________________ ________________-

hypothalamus; negative feedback

luteinizing hormone (LH)

in males has been referred to as interstitial cell stimulating hormone (ICSH), promotes development of interstitial cells of the testes, and they, in turn, secrete male sex hormones.

Compared to the overall size of the ovary, the mature antral follicle...

is so large that no matter where the secondary oocyte is released from the ovary, it will contact the branched extensions (fimbriae) of the associated uterine tube. If the secondary oocyte is not fertilized within hours, it degenerates.

The internal accessory organs of the male reproductive system are specialized to...

nurture and transport sperm cells.

Chromosomes

one set of genetic instructions, carried on 23 chromosomes, compared to other cells of the body which have two sets on 46 chromosomes

A lobule contains...

one to four highly coiled, convoluted seminiferous tubules, each approximately 70 centimeters long uncoiled.

Of the six to seven million primary oocytes that formed in the embryonic ovary...

only a million or so remain at birth, and perhaps 300,000 are present at puberty. Of these, probably fewer than 300 to 400 oocytes will be released from the ovary during a female's reproductive life.

uterine tubes (fallopian tubes or oviducts)

open near the ovaries Each tube is about 10 centimeters long and 0.7 centimeters in diameter, passes medially to the uterus, penetrates its wall, and opens into the uterine cavity. Simple columnar epithelial cells, some ciliated, line the uterine tube epithelium secretes mucus, and the cilia beat toward the uterus. These actions help draw the secondary oocyte and expelled follicular fluid into the infundibulum following ovulation. connect at the upper lateral edges of the uterus expands, forming a funnel-shaped infundibulum

follicular cells

organize into layers, and eventually a cavity (antrum) appears in the cellular mass. The structure is now called an antral follicle. A clear follicular fluid fills the antrum

prepuce (foreskin)

originates just posterior to the glans and extends anteriorly to cover it as a sheath circumcision removes the prepuce.

head of a sperm cell

oval is primarily composed of a nucleus and contains highly compacted chromatin consisting of 23 chromosomes.

testes

ovoid structures about 5 centimeters in length and 3 centimeters in diameter. Both testes are within the cavity of the saclike scrotum.

During sexual stimulation...

parasympathetic impulses from the sacral part of the spinal cord cause the release of the neurotransmitter nitric oxide (NO)

ejaculatory duct

passes through the prostate gland and empties into the urethra. formed from the ductus deferens uniting with the duct of a seminal vesicle

puberty

phase in development, when an individual becomes reproductively functional Between the ages of thirteen and fifteen, a young man's androgen production usually increases rapidly.

ovulation

releases these cells from the mature antral follicle. Release of LH from the anterior pituitary gland plays a role in triggering ovulation, during which the mature antral follicle swells and its wall weakens.

secondary oocyte

resulting from division is large

first polar body

resulting from division is small

sustentacular cells

secrete a hormone called inhibin

When a sperm and an oocyte join at fertilization...

the amount of genetic information held in 46 chromosomes is restored

At the end of meiosis... (female)

the chromosomes from the sperm combine with those of the ovum, and the ovum becomes a zygote

when a primary oocyte divides...

the cytoplasm is distributed unequally

Meiosis includes two successive divisions

the first and second meiotic divisions.

Primary sex organs (male)

(gonads) of the male reproductive system are the two testes, in which sperm cells develop and the male sex hormones are synthesized.

primary sex organs (female)

(gonads) of this system are the two ovaries, which produce the female sex cells and sex hormones

Secondary sex characteristics in the male include...

1. increased growth of body hair, particularly on the face, chest, axillary region, and pubic region; growth of hair on the scalp may slow 2. enlargement of the larynx and thickening of the vocal folds, with lowering of the pitch of the voice 3. thickening of the skin 4. increased muscular growth, broadening of the shoulders, and narrowing of the waist 5. thickening and strengthening of the bones

sperm cell

A mature sperm cell is a tiny, tadpole-shaped structure about 0.06 millimeters long. It consists of a flattened head, a cylindrical midpiece (body), and an elongated tai

acrosome

A small protrusion of its head and contains enzymes that aid the sperm cell in penetrating the layers surrounding the oocyte during fertilization

oocytes

Female sex cells which in Latin means "egg cells." transport these cells to the site of fertilization provide a favorable environment for a developing offspring move the offspring to the outside; and produce female sex hormones.

primary oocyte

within the mature antral follicle is a large, spherical cell, surrounded by a layer of glycoprotein called the zona pellucida, with layers of follicular cells called the corona radiata

spermatogenesis

Sperm cell production occurs continually in a male, starting at puberty. The resulting sperm cells collect in the lumen of each seminiferous tubule, and then pass to the epididymis, where they accumulate and mature.

orgasm (male)

The culmination of sexual stimulation pleasurable feeling of physiological and psychological release. Orgasm in the male is accompanied by emission and ejaculation.

polar bodies

Their role in reproduction allows for production of an oocyte that has not only just the haploid number of chromosomes but also the massive amounts of cytoplasm and the abundant organelles required to carry the zygote through the first few cell divisions.

seminiferous tubules

These tubules course posteriorly and unite to form a complex network of channels that give rise to several ducts that join a tube called the epididymis lined by specialized stratified epithelium with spermatogenic cells (germ cells)

sperm cells usually do not move independently until...

after ejaculation.

prostate-specific antigen (PSA)

an enzyme that helps liquefy semen.

Ovarian tissues

are divided into two indistinct regions—an inner medulla and an outer cortex

accessory sex organs (secondary sex organs) of the female reproductive system

are the internal and external reproductive organs

accessory sex organs (secondary sex organs) of the male reproductive system

are the internal and external reproductive organs

bulbourethral glands

each about a centimeter in diameter and are inferior to the prostate gland composed of many tubes whose epithelial linings secrete a mucuslike fluid in response to sexual stimulation.

ejaculation

In response, motor impulses are conducted from the spinal cord to certain skeletal muscles at the base of the penile erectile columns, rhythmically contracting them. This increases the pressure in the erectile tissues and aids in forcing the semen through the urethra to the outside At the time of ejaculation, the posterior pituitary gland releases a burst of oxytocin, which stimulates contractions of the epididymides, seminiferous tubules, and prostate gland, aiding the movement of sperm.

androgens

Male sex hormones produced many by the Interstitial cells of the testes small amounts are synthesized in the adrenal cortex

prostate gland

a chestnut-shaped structure about 4 centimeters across and 3 centimeters thick that surrounds the proximal part of the urethra, just inferior to the urinary bladder enclosed in connective tissue and composed of many branched tubular glands whose ducts open into the urethra. secretes a thin, milky fluid - includes citrate and prostate-specific antigen (PSA)

penis

a cylindrical organ that conveys urine and semen through the urethra to the outside During erection, it enlarges and stiffens, enabling it to be inserted into the vagina during sexual intercourse.

fructose

a monosaccharide that provides energy to sperm cells

citrate

a nutrient for the sperm

The internal accessory organs of the female reproductive system include...

a pair of uterine tubes a uterus a vagina

scrotum

a pouch of skin and subcutaneous tissue that hangs from the lower abdominal region posterior to the penis A medial septum divides the scrotum into two chambers, each which encloses a testis Each chamber contains a serous membrane that covers the testis protects and helps regulate the temperature of the testes

capacitation

a process that results in a weakening of the sperm cells' acrosomal membranes.

Testosterone secretion...

begins during fetal development and continues for several weeks following birth; then it nearly ceases during childhood. Between the ages of thirteen and fifteen, a young man's androgen production usually increases rapidly After puberty, testosterone secretion continues throughout the life of a male.

erection

blood accumulates in the erectile tissues, and the penis swells and elongates results from increasing pressure of arterial blood entering the vascular spaces of erectile tissue compresses the veins of the penis, reducing the flow of venous blood away from the organ

gonadtropins

called luteinizing hormone (LH) and follicle-stimulating hormone (FSH).

epididymis

coiled on the outer surface of the testis and continues to become the ductus deferens

Reproductive System

connected sets of organs that produce and nurture sex cells (gametes) and transport them to sites of fertilization function is the secretion of hormones vital to the development and maintenance of reproductive organs and the regulation of reproductive functions.

ovarian cortex

consists of more compact tissue and has a granular appearance due to tiny masses of cells called ovarian follicles.

tail (flagellum) of a sperm cell

consists of several microtubules enclosed in an extension of the cell membrane. The mitochondria provide ATP for the tail's lashing movement that propels the sperm cell through fluid.

seminal vesicles

convoluted, saclike structures about 5 centimeters long. Each attaches to a ductus deferens on the posterior surface and near the base of the urinary bladder

glans penis

covers the ends of the corpora cavernosa and bears the urethral opening (external urethral orifice). The skin is very thin and hairless, and contains sensory receptors for sexual stimulation. A loose fold of skin called the prepuce (foreskin) originates just posterior to the glans and extends anteriorly to cover it as a sheath

interstitial cells (cells of Leydig)

lie in the spaces between the seminiferous tubules Interstitial cells produce and secrete male sex hormones.

spermatids

mature into sperm cells

Primary follicles

matured from primordial follicles

At puberty...

mitosis resumes, and new spermatogonia form Testosterone secretion increases and the primary spermatocytes then reproduce by a special type of cell division called meiosis

ovarian medulla

mostly composed of loose connective tissue and contains many blood vessels, lymphatic vessels, and nerve fibers

ductus deferent (vasa deferentia)

muscular tubes about 45 centimeters long Each ductus deferens passes upward along the medial side of a testis and through a passage in the lower abdominal wall (inguinal canal), enters the pelvic cavity, and ends behind the urinary bladder.

prostsate cancer

nearly 240,000 men receive a diagnosis of prostate cancer and about 30,000 men die of the disease secretory epithelium in the prostate gland releases PSA, which liquefies the ejaculate. When cancer cells accumulate, more PSA is produced, and it enters capillaries in the prostate.

nitric oxide (NO)

neurotransmitter that dilates the arteries leading into the penis, increasing blood flow into erectile tissues

seminal vesicle fluid

neutralizes the acidic secretions of the vagina, helping to sustain sperm cells that enter the female reproductive tract. Seminal vesicle secretions also include fructose and prostaglandins aiding the movement of sperm cells toward the oocyte.

hypothalamus, anterior pituitary gland, and testes

secrete hormones that control male reproductive functions initiate and maintain sperm cell production, and oversee the development and maintenance of male secondary sex characteristics, which are special features associated with the adult male body.

gonadotropin-releasing hormone (GnRH)

secreted by the hypothalamus enters the blood vessels leading to the anterior pituitary gland.

serous membrane

secretes serous fluid, which reduces friction as the testis moves within the scrotum.v

The first meiotic division (meiosis I)

separates homologous chromosome pairs.

glandular tissue lining the inner wall of a seminal vesicle secretes a __________________________. This fluid helps regulate...

slightly alkaline fluid the pH of the tubular contents as sperm cells travel to the outside

ovaries

solid, ovoid structures, each about 3.5 centimeters long, 2 centimeters wide, and 1 centimeter thick. The ovaries lie in shallow depressions in the lateral wall of the pelvic cavity A layer of cuboidal epithelium covers the ovary's free surface. Just beneath this epithelium is a layer of dense connective tissue.

prostaglandins

stimulate muscular contractions within the female reproductive organs aid the movement of sperm cells toward the oocyte.

follicle-stimulating hormone (FSH)

stimulates the sustentacular cells of the seminiferous tubules to respond to the effects of the male sex hormone testosterone

Sustentacular cells

support, nourish, and regulate the spermatogenic cells.

The epithelium of the seminiferous tubules consists of...

sustentacular cells (Sertoli cells) and spermatogenic cells.

Immediately after ejaculation...

sympathetic impulses constrict the arteries that supply the erectile tissue, reducing inflow of blood. Smooth muscle in the walls of the vascular spaces partially contracts, and the veins of the penis carry excess blood out of these spaces. The penis gradually returns to its flaccid state

Semen

the fluid the male urethra conveys to the outside during ejaculation. consists of sperm cells from the testes and secretions of the seminal vesicles, prostate gland, and bulbourethral glands. Semen is slightly alkaline (pH about 7.5), and it includes prostaglandins and nutrients. volume of semen released at one time varies from 2 to 5 milliliters. The average number of sperm cells in the fluid is about 120 million per milliliter.

testosterone

the most important androgen secreted by the testes and transported in the blood, loosely attached to plasma proteins.

emission

the movement of sperm cells from the testes and secretions from the prostate gland and seminal vesicles into the urethra, where they mix to form semen a response to sympathetic impulses from the spinal cord, which stimulate peristaltic contractions in smooth muscle in the walls of the testicular ducts, epididymides, ductus deferentia, and ejaculatory ducts.

oogenesis

the process of oocyte formation. Beginning at puberty, some primary oocytes are stimulated to continue meiosis. Like sperm cells, the resulting cells have one-half as many chromosomes (23) in their nuclei as their parent cells.

After ovulation...

the secondary oocyte and one or two layers of follicular cells surrounding it are normally propelled to the opening of a nearby uterine tube

If fertilization occurs...

the secondary oocyte undergoes the second meiotic division and divides unequally to produce a tiny second polar body and a large ovum

in the presence of FSH and testosterone...

the sustentacular cells stimulate spermatogenic cells to undergo spermatogenesis, giving rise to sperm cells

These internal accessory organ structures include...

the two epididymides two ductus deferentia two ejaculatory ducts urethra as well as the two seminal vesicles the prostate gland two bulbourethral glands.

spermatogonia

the undifferentiated spermatogenic cells in the male embryo Each contains 46 chromosomes (23 pairs) in its nucleus hormones stimulate spermatogonia to undergo mitosis during embryonic development

When sperm cells reach the epididymis...

they are nonmotile

A tough, white, fibrous capsule encloses each testis. Along the capsule's posterior border, the connective tissue thickens and extends into the testis, forming...

thin septa that divide the testis into about 250 lobules.

corpus spongiosum

through which the urethra extends enlarges at its distal end to form a sensitive, cone-shaped glans penis.

epididymides

tightly coiled tubes about 6 meters long Each is connected to ducts within a testis. It emerges from the top of the testis, descends along the posterior surface of the testis, and then courses upward to become the ductus deferens.