Biology 30 Human Reproduction & Development

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Biology 30Human Reproduction

& Development Anatomy of the Male and Female

Reproductive Systems Gamete Formation

Hormonal Control of Reproduction Conception, Pregnancy, Development, Birth

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Biology 30

Male Reproductive Anatomy

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You solve the problem. “Recently I have experienced my right

testicle slipping upwards into my body and ‘disappearing’. It can be felt through the skin, and then can be slid back down. The only pain is a dull ache that ensues. It seems to require some pressure on the scrotum to occur, such as my wife being ‘frisky’. Is there a term and/or a treatment for this? Is it serious?”

December 7, 1999

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External genitalia– Penis and Scrotum

Internal Reproductive Organs– Pair of gonads

Produce gametes (sperm cells) Produce hormones

– Accessory glands Secret products essential to sperm

movement– Set of ducts

Carry sperm and glandular secretions.

Anatomy of the Male Reproductive System

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Penis– Composed of 3 cylinders of spongy

tissue.– During sexual arousal, tissue fills with

blood from the arteries The increasing pressure seals off the veins

that drain the penis– Result = penis engorges with blood = erection

– The tip (Glans) is covered by a fold of skin called the foreskin, which may be removed by circumcision A tradition with religious roots. No verifiable health or hygienic advantage.

Anatomy of the Male Reproductive System

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Scrotum– Sac which contains testes– Regulates temperature of testes by

contraction of cremaster muscle. Cold = contracts

– Brings testes close to body to warm up. Warm = relaxes Goal = keep testes 3o below normal body

temperature.

Anatomy of the Male Reproductive System

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Testes– Stored in scrotum

Before birth, testes develop in the abdomen and then migrate down a canal into scrotum around the time of birth.

– Sperm producing organ Made in tightly coiled tubes called seminiferous

tubules inside testes Sperm produced is not fully mature when it leaves

testis (not motile yet)– Source of male hormone testosterone

Made by interstitial cells scattered between the seminiferous tubules

– Deposits sperm into epididymis

Anatomy of the Male Reproductive System

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Epididymis– Coiled tubes– About 6 meters long!!– Posterior to the testis– Stores sperm– Site of further sperm maturation

Gains motility– Contracts during ejaculation, expelling

sperm into vas deferens– Sperm can be store here for months

If not ejaculated, will eventually be phagocytized

Anatomy of the Male Reproductive System

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Vas Deferens– Muscular tubes that carry sperm from

epididymis to ejaculatory duct (and eventually the urethra) peristalsis

– Urethra drains both the excretory system and the reproductive system Not the case in females

Anatomy of the Male Reproductive System

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Ejaculatory Duct– Connects seminal vesicle to urethra– Passes through prostate gland

Anatomy of the Male Reproductive System

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Seminal Vesicle– Lies below and behind bladder– Secretes thick, clear fluid into

ejaculatory duct 60% volume of semen (the fluid that is

ejaculated) Alkaline – to neutralize acidic pH of vagina Fructose – used for energy by sperm Prostaglandins – chemical messengers

which, once in female, stimulate uterine peristalsis to help move semen up the uterus

Proteins – cause semen to coagulate after it is deposited in the female, making it easier for the uterine contractions to move the semen

Anatomy of the Male Reproductive System

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Prostate Gland– Doughnut shaped gland which surrounds

urethra– Secretes thin milky fluid into urethra

20% of seminal volume Liquefy the semen – prevents sperm from

clumping together Alkaline – continues to neutralize acid from

residual urine in urethra and natural acidity of vagina

Prostate Source of most common medical problems of men over 40. Benign enlargement in over ½ of all men in the age group.

Anatomy of the Male Reproductive System

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Cowper’s Gland (Bulbourethral Gland)– Pair of small glands along urethra,

below the prostate– Secrete viscous fluid before emission of

sperm & semen Thought to lubricate penis and vagina

– Released before ejaculation Fluid does contain some sperm One factor in the high failure rate of the

“withdrawal method” of birth control.

Anatomy of the Male Reproductive System

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Vasectomy– Incision through scrotum– Cut and tie off vas deferens– Sperm is still produced but can’t get out– Phagocytized– Increased risk of prostate cancer

Anatomy of the Male Reproductive System

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Passageway from testes to outside1. Multiple seminiferous tubules

site of spermatogenesis2. Single tubed epididymis3. Vas deferens4. Seminal vesicle5. Ejaculatory duct6. Urethra

Anatomy of the Male Reproductive System

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For Your Information– Volume of ejaculation = 2.75 ml– pH = 7.2 – 7.6– 50 – 150 million sperm per ml.– Only a few sperm reach the egg– Average sperm count has decreased from

113 million/ml to 66 million/ml in past 40 years.

– Infertility = <20 million/ml Factors leading to infertility are

environmental toxins, estrogens in meat, radiation,pesticides, marijuana, alcohol

Anatomy of the Male Reproductive System

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Solution to the medical problem.

Remember that before birth, the testes develop in the abdomen, and then migrate down into the scrotum at birth. The pathway they follow through the layers of the abdominal wall on each side is called the inguinal canal. Usually, when the testes have completed their descent they remain permanently within the scrotum from that time on. The slightly lower temperature in the scrotum is more favorable to sperm production after puberty. Slender bundles of muscle fibers derived from the middle layer the abdominal muscle are

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Solution to the medical problem.

drawn into loops around the descending testis and form what is know as the cremaster muscle. During sexual arousal, the smooth muscle of the scrotum contracts too. As a result, the testes are transiently held in a more protected position during sexual intercourse. It is possible that your right testis has remained more mobile that usual, and is drawn back partially in the to inguinal cal by contraction of the cremaster muscle during sexual activity. This is referred to as

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Solution to the medical problem.

a “retractile testis”. If you at all concerned about this possibility, it will be worthwhile visiting your doctor to discuss the situation and whether or not any treatment is required.

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Labelling Diagram1. Pubic Bone2. Seminal Vesicles3. Rectum4. Prostate Gland5. Cowper’s Gland6. Anus7. Vas Deferens (sperm duct)

8. Epididymis9. Testes10.Urethra11.Penis12.Scrotum13.Head of Penis (Glans)14.Foreskin15.Bladder

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Biology 30

Female Reproductive Anatomy

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Consists of: External genitalia

– Two sets of labia that surround the clitoris and vaginal opening

Internal Reproductive Organs– A pair of gonads (ovaries)– A system of ducts and chambers to

Conduct the gametes House the embryo and fetus

Anatomy of the Female Reproductive System

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Ovaries– Lie in abdomen, below most of

the digestive system– Enclosed in a tough protective

capsule– Produces eggs (follicles)– Produces female sex hormones

1. Estrogen2. Progesterone

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Follicles– Consists of one egg cell surrounded by

layers of follicle cells. Nourish and protect the developing egg

cell– All of the 400,000 follicles a woman

will ever have are present at birth. Only a few hundred will be released during

a woman’s reproductive years One (very rarely 2 or more) follicle matures

and releases its egg during each menstrual cycle

Anatomy of the Female Reproductive System

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Follicles– Follicle cells release the primary

female sex hormone… estrogen. Secondary sex characteristics, wider hips, more

body fat, Necessary for breast development

– At ovulation, the egg “explodes” out of the follicle leaving behind the follicular tissue This grows into a solid mass called a Corpus Luteum

– Secretes progesterone (necessary for pregnancy)

If fertilization does not occur, the corpus luteum disintegrates and a new follicle matures the next month.

Anatomy of the Female Reproductive System

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Oviduct– Fallopian tube– Conducts eggs to the uterus– Fertilization occurs here

If embryo grows here = ectopic pregnancy– The ovary and oviduct don’t actually touch.– The egg is released into the abdominal cavity

and is “sucked” into the oviduct. Oviduct has fingers called “fimbrae” and

hairs called “cilia” that vibrate and sweep the egg into the tube by swishing body fluids towards itself

These cilia also help move the egg towards the uterus

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Uterus (womb)– Houses and nurtures the developing

fetus– Oviducts enter at the top– Cervix (opening) at the bottom– The lining is called the endometrium

Richly supplied with blood vessels Varies in thickness depending on the stage

of the menstrual cycle Controlled by hormones 2 Layers

– Basal layer = stable, does not change thickness– Functional layer = changes thickness with

menstruation

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Vagina– Birth canal– Average = 7.5 cm in length– pH = 4-5– Upper end closes at cervix– Receives penis during sexual

intercourse– Elastic to facilitate sexual intercourse

and birth

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Biology 30

Gamete Formation

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Need– The human body cell contains 46

chromosomes that are paired together 23 pairs Called diploid cells

– If 2 diploid (means 46 chromosomes) cells fuse the result would be … 92 chromosomes (46 pairs) Chromosome number would increase exponentially

– Sperm and egg must contain 23 chromosomes each in order to maintain appropriate chromosome count

– Haploid = ½ the normal chromosome count23 chromosome sperm +23 chromosome egg = 23

pairs

Gamete Formation

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Spermatogenesis– Each ejaculation = 400 million sperm– Males can ejaculate daily without loss

of fertility– Occurs in the testes

Gamete Formation

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Gamete Formation Spermatogenesis

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Gamete Formation Spermatogenesis

1. The walls of the seminiferous tubules consist of diploid spermatogonia, stem cells that are the precursors of sperm.

2. divide by mitosis to produce more spermatogonia

3. The Meiosis of each spermatocyte produces 4 haploid spermatids.

4. These then differentiate into sperm, losing most of their cytoplasm and gaining motility in the process.

In epididymis Sperm nourished by

sertoli cells (in seminiferous tubules)

Whole process takes 70 days

Gamete Formation -- Spermatogenesis

1. Takes place in ovaries2. Primary Oogonium

develop into oocytes before birth

3. Oocytes complete maturation one at a time & once a month during reproductive years

4. Primary oocyte grows larger and begins meiosis

5. Forms a secondary oocyte and first polar body

6. After fertilization, secondary oocyte completes meiosis and become 1 egg and second polar body.

Gamete Formation -- Oogenesis

Before Birth

Once a month

If Pregnant

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Follicles– Consists of one egg cell surrounded by layers

of follicle cells.– Nourish and protect the developing egg cell – Follicle cells release the primary

female sex hormone… estrogen.– At ovulation, the secondary oocyte

“pops” out of the follicle leaving behind the follicular tissue This grows into a solid mass called a Corpus Luteum

– Secretes progesterone (necessary for pregnancy)

If fertilization does not occur, the corpus luteum disintegrates and a new follicle matures the next month.

Recap of Follicles

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ReviewComplete Lessons 1 & 2

from your Unit Objectives Package