Biology 12

Male Reproductive System

A. Testes Male gonads (gamete producing organ) Develop in abdomen but descend into scrotum through

_________ __________ during development—____________ is condition when they do not

Scrotum allows for cooler temperatures needed for sperm development (about 2-3°C below body temperature)

(i) Seminiferous Tubules Produce sperm—___________________ Sperm produced throughout entire lifetime of male

Figure 1: Cross Section of Testes

Cells found in seminiferous tubule according to developmental stages are:

a) _______________ (2n)— cells that divide mitotically to form:b) ___________ ____________ (2n x2)—diploid cell (46 pairs of

homologous chromosomes) that undergo meiosis (i.e. meiosis I) to form 2:

c) _________ ____________ (2n)—each has 23 pairs of chromosomes and divides (meiosis 2) to form 4:

d) __________ (n)—each having 23 chromosomes at end of 2nd meiotic division forming:

e) _____________ (n)—has 23 chromosomes; nourished and supported by Sertoli cells (aid sperm cells through development)

Stages of Spermatogenesis:

Sperm Anatomy:

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(ii) Interstitial Cells (Leydig cells) Secrete ____________ under influence of LH from anterior

pituitary

(iii) Sertoli Cells (sustentacular cells) Nourish developing sperm cells

B. Epididymis

Where sperm mature and gain ability to swim and fertilize egg Moved to vas deferens by contractions of smooth muscles in

epididymis

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Head—contains 23 chromosomes in a nucleus

Acrosome— covers head and contains enzymes that help penetrate the egg

Midpiece or Mitochondrial sheath—contains mitochondria to produce energy for sperm motility

Tail—contains 9 + 2 microtubule arrangement for motility

Figure 2: Epididymis

C. Vas Deferens Vas deferens passes through inguinal canal into abdomen and

empties into __________

D.Spermatic Cords

Suspend testes in scrotum

Figure 3: Spermatic cords

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Hernia— when abdominal contents are pushed through the inguinal canal and into the scrotum; e.g. small intestine.

E. Penis Made of:

(i) Glans penis Cone-shaped terminal portion of penis covered with

prepuce or foreskin

(ii) Foreskin Glands in foreskin produce secretion called smegma Keeps glans moist and lubricates movement of foreskin

(iii) Erectile Tissue Parasympathetic N.S. → dilates arteries in erectile

tissue and compresses veins → results in tiny spaces in erectile tissue filling with blood → erection

____________ is condition that results from erectile difficulties

Impotency can be indicative of other underlying problems with circulation

F. Seminal Fluid (Semen)5

Produced by seminal vesicles, prostate gland and Cowper’s or bulbourethral gland

Fluid is milky in appearance and slightly basic (pH 7.5) Contains __________ (for sperm energy) ___________ (cause

contraction of uterus)

(i) Seminal Vesicles Each joins vas deferens via ejaculatory duct as vas enters

urethra Produces prostaglandins, fructose, proteins, enzymes and

other chemicals that form semen

(ii) Prostate Gland

Also contains smooth muscle that helps move sperm during ejaculation

enlarged prostate→ constrict urethra→ difficulty urinating

(iii) Cowper’s Gland (Bulbourethral Glands)

Also neutralizes acid urine remnants in urethra Helps flush out residual urine or foreign matter in urethra Also can pick up previous sperm in urethra from previous

ejaculations and carry them out before next ejaculation

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Figure 4: Cowper’s, Prostate Glands and Seminal Vesicles

G.Ejaculation Sperm and fluid from the accessory organs combine during

sexual stimulation, which is then expelled (ejaculation from penis during orgasm

In males refractory period occurs after ejaculation → cannot

get another erection for about 15 -20 minutes or longer

H.Path of Sperm During Ejaculation Seminiferous tubules → epididymis → vas deferens →

ejaculatory duct → prostate gland → urethra→ ejaculation

I—Hormonal Control of Male Reproduction

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_____________→ _______ (gonadotropic releasing hormone→ stimulates ________ ________ to release→ ____ (follicle stimulating hormone) → and LH (leutinizing hormone)

FSH and LH are collectively called ______________ hormones

a) FSH →_______________ in seminiferous tubules (sertoli cells can produce hormone ________—inhibits FSH secretion and GnRH secretion (negative feedback loop)

b) LH → ____________ production by interstitial cells of testes (when testosterone levels ↑, negative feedback established with anterior pituitary and hypothalamus to decrease LH production

Diagram of hormonal control of testes and hormone/sperm production

J—Testosterone

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Maturation of sperm Secondary sex characteristics: beard, body hair, voice change

and ↑ muscle mass and strength

K—Female Reproductive System

Diagram of Internal Reproductive System In Females

A. Ovaries Held close to oviducts by suspensory ligaments which are

attached to walls of the uterus9

Each month ovaries produce an egg that bursts from ovary during ____________

B. Oviducts (Fallopian Tubes)

Contain __________—at opening near ovaries which are

finger-like projections that sweep up eggs from ovary Muscular contractions and cilia lining fallopian tubes waft

egg toward uterus

Tubular pregnancies occur when embryo implants in oviduct Ectopic pregnancy is any implantation outside central body

of uterus can also occur

C. Uterus Size and shape of inverted flattened pear Lies above and slants forward over urinary bladder Cervix of uterus is opening of uterus that enters vagina at

right angle posteriorly ______________ lining forms placenta with ______ ______

(below functional layer) and _________ _____ (closest to uterine cavity) this is the layer that varies with uterine cycle

Cancer of the cervix usually detected by Pap smear ____________ (removal of uterus) if cancer found

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D. Vagina Tube with mucosa lining Makes 45 degree angle with small of back Serves in intercourse Wall extends greatly as birth canal

E. Female External Genitalia Vulva is collective term for external genitalia Mons pubis is fatty prominence under pubic hair Labia majora enclose following structures: Labia minora extend from vaginal opening to encircle

clitoris at front Clitoris is homologous to penis, contains erectile tissue Hymen is ring of tissue that may partially close vaginal

opening See page 397 in text

L—Female Hormone Levels

hypothalamus→ ________ → anterior pituitary → ____ + ___ (gonadotropic hormones)

______ → stimulates follicular development in ovary which secretes mostly estrogen and some progesterone

_____ → involved in uterine cycle and development of corpus luteum which secretes mostly progesterone and some estrogen

__________ __________ produce and secrete sex hormones: estrogen (and some progesterone)

Gonadotropic and sex hormones secreted at different rates depending on ovarian cycle

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M—Ovarian Cycle

Occurs in ovaries Results in production of egg (oocyte)—__________ Females have about 2 million _________ _______ just before

birth (around month 7 of gestation) that have begun meiosis I and have stopped at Prophase I. By birth, most will have degenerated and only about 3-4 hundred thousand will remain.

These oocytes in the ovaries are surrounded by cells called follicular cells.

Synopsis of Ovarian Cycle: Involves the development of an _________ __________, the release of an _____ (egg) and the formation and regression of a _________ _________

Note: follicle cells support and nourish an oocyte

Oogenesis

Figure 1: Oogenesis and Ploidy

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Diagram of Ovarian Cycle

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Follicular Phase (weeks 1-2)

Week 1-2: One primary oocyte in ovary completes meiosis I to form two

cells: ________ ________ and _____ ______ _______ (both 4n) One of these cells (first polar body) degenerates and the other cell

remains in the follicle to become the ___________ _______—the follicle is also called the ___________ _________ since it is surrounded by follicular cells

Follicle cells secrete sex hormone __________ and a little _____________ throughout this period of time

The secondary oocyte begins meiosis II during this phase as well but stops at metaphase II

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Follicle grows in size as result of continuing ____ secretions from anterior pituitary→ enlarges to eventually become ___________ ________

Graafian follicle grows in size to form a bulge that merges with walls of ovary and bursts releasing secondary oocyte--________

Secondary oocyte (egg) is surrounded by mucoprotein substance called ______ ___________ and some __________ ______

The zona pellucida contains material that allows acrosomal enzymes to function and it helps to “bind sperm” to egg

Once a follicle has lost egg, it becomes the _______ ________— a hormone releasing structure

As ___________ levels rise in follicular stage→ negative feedback on anterior pituitary → ↓ FSH → follicular phase stops

At time of ovulation however, an estrogen spike occurs causing a spike of GnRH from the hypothalamus→ this spike in GnRH causes the anterior pituitary to ↑↑ _____ & ___ secretions (especially LH)

Note: Both LH & FSH subsequently decrease in concentration due to negative feedback of estrogen and progesterone on anterior pituitary and hypothalamus

Luteal Phase (Weeks 3-4):15

LH encourages development of _________ __________ Corpus luteum secretes ____________ → stimulate development

of uterus needed for sustaining embryo in case of pregnancy As [progesterone] ↑ → negative feedback on anterior pituitary &

hypothalamus→ decreased LH production → degeneration of corpus luteum → luteal phase eventually over → bursting of blood vessels and degeneration of uterine lining → menstruation

Uterine Cycle

Day 1-5:

Blood vessels rupture leading to menstruation or bleeding

Day 6-13: Endometrium becomes thicker and more vascular due to

increased [estrogen]→ _______________ ______ of uterine cycle

Day 14: Ovulation occurs

Day 15-28:

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↑ [progesterone] by corpus luteum causes ___________ (inner lining of uterus) to double in thickness and uterine glands to mature producing thick mucus secretion—____________ _______ of uterine cycle

If not pregnant, corpus luteum degenerates → lower hormone

levels cause uterine lining to break down

Graph of Uterine and Ovarian Cycles

If Pregnancy Occurs:17

Fertilized egg → embeds itself in endometrial lining days after fertilization→ placenta forms from both maternal and fetal tissues → provides exchange of molecules between fetal and maternal blood

Placenta first produces ____ (human chorionic gonadotropic hormone)→ maintains corpus luteum → prevents degeneration of corpus luteum and prevents drop in estrogen and progesterone

Estrogen and progesterone shut down anterior pituitary thus no new follicles mature and menstruation stops

Oxytocin

Causes smooth muscle contraction in uterus →can also be used to induce labour

Fetal Circulation

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Prior to birth the placenta is responsible for waste removal, gas exchange and nourishment of the fetus.

Lungs and liver not in use yet To accomplish this there are four features in fetal circulation

which are not present in an adult.

1. The ________ ______ and ________ carry blood to and from the embryo.

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Blood full of waste material and carbon dioxide on the other hand leaves fetus via umbilical artery → placenta → mother

2. The foramen ovale or oval opening (between the right & left atria)

3. Ductus arteriosus or atrial duct.

4. The ductus venosus or venus duct

permits much of the blood to bypass the liver

Note: At birth a flap of tissue on the oval opening normally covers the oval window; also the fetal vessels mentioned above close. A failure of the tissue flap to close the oval opening could lead to a “blue baby” condition.

See page 431 in text for diagrams

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