A&PII Exam 4

Scrotum

a sac of loose skin and underlying subcutaneous tissue that contains the testes

Internally, the scrotum is separated into two compartments by

the dartos muscle and a subcutaneous layer

Testes

paired, oval glands in the scrotum partially covered by the tunica vaginalis

Internal to the tunica vaginalis is a connective tissue capsule

the tunica albuginea that extends inward to form septa that create compartments

Seminiferous tubules carry

sperm produced within them (spermatogenesis) out of the testes

Spermatogenesis begins with

spermatogonia (diploid stem cells) that differentiate into diploid primary spermatocytes

The primary spermatocyte undergoes

meiosis I to become two secondary spermatocytes (haploid)

Meiosis II takes place and the

secondary spermatocytes become four spermatids

Sperm

designed to reach and penetrate the secondary oocyte in order to achieve fertilization and create a zygote

The head of sperm contains a

nucleus with 23 chromosomes

The acrosome covers the

head and contains enzymes to help with penetration

The neck of sperm contains

centrioles that form the microtubules that make up the rest of the tail

The middle piece of sperm contains

mitochondria that make ATP for locomotion of the sperm

The principal piece and end piece of sperm make up the

tail used for movement

At puberty gonadotropin releasing hormone stimulates cells in the

anterior pituitary gland to produce luteinizing hormone and follicle stimulating hormone

luteinizing hormone stimulates cells in the

testes to produce testosterone

follicle stimulating hormone stimulates

spermatogenesis

Testosterone and dihydrotestosterone produce several effects

o Prenatal development

o Development of male sexual characteristics

o Development of sexual function

o Stimulation of anabolism

A negative feedback system controls the blood level of

testosterone

Sperm and fluid travel from the

seminiferous tubules to straight tubules and then to a network of ducts, the rete testis

Efferent ducts carry the sperm to the

epididymis

Sperm mature in the

epididymis and degenerated sperm are reabsorbed

The epididymis propels

sperm into the ductus (vas) deferens

The ductus (vas) deferens exits the tail of the

epididymis and ascends through the spermatic cord into the pelvis, then it loops over the ureter and passes over the side and down the posterior surface of the urinary bladder

The spermatic cord ascends out of the

scrotum and contains the ductus deferens, testicular artery, veins draining the testes, autonomic nerves, lymphatic vessels and the cremaster muscle

The spermatic cord and ilioinguinal nerve pass through the

inguinal canal which originates at the deep inguinal ring and ends at the superficial inguinal ring

The ejaculatory ducts arise from the junction of the duct from the

seminal vesicle and the ampulla of the ductus deferens

The urethra is the duct shared by the

reproductive and urinary systems

Both semen and urine pass through the

urethra

The urethra passes through the

prostate gland (prostatic urethra), deep muscles of the perineum (membranous urethra), and the penis (spongy urethra)

Seminal vesicles (glands)

secrete an alkaline, viscous fluid containing fructose, prostaglandins and clotting proteins

Prostate

a single, donut-shaped gland that secretes a milky, slightly acidic fluid containing citric acid, proteolytic enzymes, acid phosphatase, and seminalplasmin

Bulbourethral (Cowper’s) glands

secrete an alkaline fluid during sexual arousal that neutralizes acids from urine and mucus for lubrication

Semen

a mixture of sperm and seminal fluid

The volume of an average ejaculate is

2.5-5 ml with 50–150 million sperm/ml

The pH of ejaculate is

7.2–7.7

Penis

contains the urethra and is a passageway for semen and urine

The penis is composed of 3 cylindrical masses

2 corpora cavernosa, 1 corpus spongiosum

Glans penis

Head of penis covered by the prepuce

An erection is brought about by

parasympathetic innervation leading to vasodilation of arterioles in erectile tissue

During an erection, Large amounts of

blood enter the tissue into dilated blood sinuses

Ejaculation is the powerful release of

semen due to sympathetic stimulation

The bulbospongiosus, ischiocavernosus, and superficial transverse perineal muscles contract to

force the semen out

Ovaries

paired glands homologous to the testes

Ovaries produce

gametes (mature into ova) and hormones (progesterone, estrogens, inhibin, relaxin)

Ovaries are supported by

broad ligament, ovarian ligament, and suspensory ligament

Ovaries consist of

• The germinal epithelium

• The tunica albuginea

• The ovarian cortex

• The ovarian medulla

germinal epithelium

covers the surface of the ovary

tunica albuginea

capsule of dense irregular connective tissue below the germinal epithelium

ovarian cortex

below the tunica albuginea and consists of ovarian follicles and stromal cells

ovarian medulla

connective tissue, blood vessels, lymphatic vessels and nerves

Ovarian follicles contain

oocytes in various stages of development, follicular cells, and granulosa cells

A mature (graafian) follicle is ready to

rupture and expel the secondary oocyte

A corpus luteum develops after ovulation when the empty follicle produces

progesterone, estrogens, inhibin, and relaxin

oogenesis

formation of gametes in the ovaries

Oogenesis begins during the

fetal period, before a female is born

Oogonia (diploid stem cells) divide by mitosis to produce

Primary oocytes

Primary oocytes undergo meiosis I to produce

Secondary oocytes

Secondary oocytes undergo meiosis II to produce

Ova

Three key differences between oogenesis and

spermatogenesis

• 1. Production of primary oocytes occurs only fetus

• 2. In primary oocytes, meiosis is arrested in late prophase I and resumes only years later (if at all)

• 3. In secondary oocytes, meiosis is arrested in metaphase II and is only completed if fertilization occurs

At birth, female presumed to have

lifetime supply of primary oocytes

Ovarian follicle

functional unit of ovary that encloses a single oocyte

Ovarian follicles are surrounded by

• Pre-granulosa cells if single layer of cells present

• Granulosa cells if more than one layer present

Each month after puberty, FSH and LH stimulate the

development of the

primordial follicles. A few start to grow, developing into primary follicles, usually only one reaches maturity

Primordial follicle

single layer of squamous pre-granulosa cells surrounding primary oocyte

Follicles have two fates:

Atresia and Ovulation

Atresia

apoptosis of oocyte and surrounding cells

99.9% of all follicles are never

recruited

Ovulation

each month after puberty, a select few primary oocytes are activated

Ovulation is caused by

high hormonal levels, especially FSH

One from this group of oocytes is

“selected” each month to become dominant follicle

Dominant follicle resumes

meiosis I just before ovulation

After division of meiosis I is completed, two haploid cells of different sizes are produced:

First polar body and secondary oocyte

First polar body

smaller cell that is almost devoid of cytoplasm

Secondary oocyte

large cell with almost all of mother cell cytoplasm and organelles

Secondary oocyte arrests in

metaphase II and will become the ovulated ovum

If not penetrated by sperm, oocyte

deteriorates

If penetrated by sperm, secondary oocyte quickly completes

meiosis II

If penetrated by sperm, secondary oocyte quickly

completes meiosis II, yielding:

Ovum and Second polar body

Ovum

large cell with enough cytoplasm to nourish fertilized egg for 6-7 day journey to uterus

Second polar body

small cell lacking cytoplasm degenerates and dies

Phase 1 of maturation

gonadotropin-independent pre-antral and the phase involves intrafollicular paracrines

Phase 2 of maturation

antral phase stimulated by FSH and LH, dominant follicle is selected, and primary oocyte resumes meiosis I

Steps in a primordial follicle becoming a primary follicle.

•Primordial follicles are squamous like cells surrounding primary oocyte become cuboidal, and oocyte enlarges; process can take about one year

• Follicle is now called primary (1°) follicle

Oocyte secretes

glycoprotein-rich substances that forms zona pellucida that encapsulates oocyte

Stages in a primary follicle becoming a secondary follicle

•Pre-granulosa follicular cells proliferate, forming stratified cuboidal epithelium around oocyte

• Primary follicle now called secondary follicle

• Granulosa cells and oocyte guide one another’s development via gap junction connections

• Connective tissue and granulosa cells condense to form theca folliculi

When more than one layer of cells are present follicular cells called

granulosa cells

Thecal cells secrete hormone in response to

LH

Secondary follicle becomes vesicular (antral) follicle

•Secondary follicle stage ends when liquid accumulates between granulosa cells forming early vesicular follicle

• Antrum continues to expand with fluid isolating oocyte

• Corona radiata sits on stalk on one side of follicle

• When follicle is full size (2.5 cm or 1 inch), it bulges from external ovary surface

• It is ready to be ovulated

• After oocyte and corona radiata are ejected, ruptured follicle transforms into glandular structure called corpus luteum

Antrum

large cavity that is formed when all fluid coalesces

Antrum distinguishes vesicular follicle from

previous follicles

Isolated oocyte with its surrounding granulosa cells called

corona radiata

The ovarian cycle includes changes that occur

during and after maturation of the oocyte

The uterine cycle involves changes in the

endometrium that prepare it for implantation of the developing embryo

Ovarian cycle is a

monthly (~28 day) series of events associated with maturation of egg

Ovarian cycle contains two phases

Follicular phase: period of vesicular follicle growth

(days 1–14)

Luteal phase: period of corpus luteum activity

(days 14–28)

Only 10–15% women have

28-day cycle

Follicular phase varies, but luteal phase is always

14 days from ovulation to end of cycle

During follicular phase, several vesicular (antral) follicles become sensitive to

FSH and are stimulated to grow

FSH levels drop around middle of

follicular phase