Reproductive Anatomy of the Human Male



Reproductive Structures

reproductive anatomy of the human male.

OVERVIEW

• External Reproductive Organs

o Scrotum

o Penis

• Internal Reproductive Organs

o Gonads – produce the gametes and hormones

o Accessory glands – secrete products essential to sperm movement

o Ducts – carry the sperm and glandular secretions

• Gametes – sperm cells

STRUCTURES

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• Scrotum – a fold outside the body wall; temperature is about 2 C below that in the abdominal cavity

o Testes – the male gonads, they consist of highly coiled tubes surrounded by several layers of connective tissue.

▪ Seminiferous Tubules – where the sperm form

▪ Leydig cells – produce testosterone and other androgens

o Epididymis – coiled tubules where the sperm become motile and gain the ability to fertilize

• Ducts

o Vas Deferens – two muscular ducts which run from the scrotum around and behind the urinary bladder, and join with ducts from the seminal vesicles

o Ejaculatory Duct – a short duct that connects the vas deferens and the urethra

o Urethra – the tube that drains both the excretory and reproductive systems; runs through the penis and opens to the outside at the top of the penis

• Accessory Glands – add secretion to the fluid that is ejaculated (semen)

o Prostate Gland

▪ Largest of the semen secreting glands

▪ Secretes directly into the urethra

o Seminal Vesicles

▪ Contributes 60% of the total volume of the semen

o Bulbourethral Glands

▪ Pair of small glands along the urethra

▪ Secrete a clear mucus that neutralizes any acidic urine remaining in the urethra

• Penis

o Composed of three cylinder of spongy erectile tissue

o Fills with blood from the arteries during sexual arousal

o Glans Penis – the head of the penis; has a much thinner covering and is more sensitive to stimulation

o Prepuce – a fold of skin that covers the human glans; may be removed by circumcision

o Baculum – a bone that is contained in and helps stiffen the penis (Possessed by some mammals such as raccoons and rodents)

• Sperm Cells

o Spermatogenesis – the production of mature sperm cells

o Structure fits function

o Acrosome – contains enzymes that help the sperm penetrate the egg

o Mitochondria – provide ATP for the movement of the tail

o Tail – flagellum; allows the sperm to move

o Mammalian sperm shape varies from species to species

Reproductive anatomy of the human female.

OVERVIEW

• External Reproductive Structures

o Clitoris

o Two sets of Labia

o Vaginal Opening

• Internal Reproductive Structures

o Gonads

o Ducts and Chambers – conduct the gametes; house the embryo and fetus

STRUCTURES

• Ovaries – female gonads; lie in the abdominal cavity and are enclosed in tough protective capsules

o Follicle

▪ consist of one egg cell surrounded by one or more layers of follicle cells, which nourish and protect the developing egg cell.

▪ A woman has around 400,000 follicle cells, all of which are formed before birth

▪ matures and releases its egg cell during each menstrual cycle

▪ produces estrogens

o Corpus Luteum

▪ A solid mass formed from the follicular tissue after the follicle releases an egg

▪ Secretes additional estrogens and progesterone

▪ Disintegrates and if the egg cell is not fertilized

o Oviduct : Fallopian Tubes

▪ Tubes with a funnel-like opening that conduct the egg cell from the ovaries to the uterus

• Uterus

o Also known as the womb

o A thick muscular organ that can expand during pregnancy to contain a 4 kg baby

o Endometrium – inner lining of the uterus; is richly supplied with blood vessels

o Cervix – the neck of the uterus; opens into the vagina

• Vagina

o A thin-walled chamber

o Birth canal through which the baby is born

o Repository for sperm during copulation

o Hymen – vascularized membrane that partly covers the vaginal opening in humans

• Vestibule - the region containing the following:

o Vaginal opening

o Urethral Opening

o Clitoris – located at the front edge of the vestibule

▪ Consists of a short shaft supporting a rounded glans covered by a small hood of skin (the prepuce).

▪ Consists largely of erectile tissue

o Labia Minora – a pair of slender skin folds that border the vestibule

o Labia Majora – a pair of thick fatty ridges which enclose and protect the labia minor and vestibule

• Glands

o Bartholin’s glands – located near the vaginal opening; secrete mucus into the vestibule during sexual arousal

o Mammary Glands – present in both sexes but normally function only in women. Secrete milk which drains into a series of ducts opening at the nipple

• Ova

o mature unfertilized egg cells

o Oogenesis: production of ova

Consists of:

o Yolk: cell substance

o Germinal vesicle: nucleus

o Germinal spot: nucleolus

o Zona pellucida: thick, transparent envelope surrounding the egg cell

o Corona radiata: surrounds the zona pellucida

o Layers of cells derived from the follicle

Human Sexual Reponse

• Human Sexuality: refers to various sexually related aspects of human life, including physical and psychological development, and behaviors, attitudes, and social customs associated with the individual's sense of gender, relationships, sexual activity, mate selection, and reproduction

Physiological Reactions

• Vasocongestion: filling of a tissue with blood caused by the increased blood flow

• Myotonia: increased muscle tension

Sexual Response Cycle

• Excitement

o Preparation for coitus: sexual intercourse

o Vasocongestion: filling of a tissue with blood caused by the increased blood flow

o Myotonia: increased muscle tension

• Plateau

o continuation of the responses in the excitement phase

o breathing, heart rate, blood pressure rise

• Orgasm

o rhythmic involuntary contractions of the reproductive structures

o Emission: contraction of glands and ducts of the reproductive tract that forces semen in the urethra

o Ejaculation: urethra contracts; semen is expelled

• Resolution

o reversal of responses of the earlier stage

QUIZ

1.Which of the following are most alike in function?

a. vas deferens - uterus

b. seminiferous tubules of testes - follicle cells of ovaries

c. epididymis - cervix

d. scrotum - corpus luteum

ANSWER: b, they are where the gametes are stored/formed.

2. Why is the scrotum located outside the abdominal wall?

ANSWER: Sperm production cannot occur at normal human body temperatures.

3-4. Give 2 out of the 3 accessory glands of the male reproductive system.

ANSWERS: Bulbourethral glands, prostate gland, seminal vesicles

5. T/F. All of the follicles a woman will ever have are formed before her birth.

6. T/F. The corpus luteum is formed when the egg is fertilized.

Name the structure being described.

7. The inner lining of the uterus, it is richly supplied with blood vessels. ANSWER: endometrium

8. The largest of the semen-secreting glands, it secretes its products directly into the urethra. Cancer of this gland is one of the most common cancers in men. ANSWER: prostate gland

9. Also known as the fallopian tube, this duct conveys the egg cell from the ovaries to the uterus. ANSWER: oviduct

10. What do you call the vascularized membrane that partly covers the vaginal opening in humans?

11. What part of the sperm contains enzymes that help the sperm penetrate the egg?

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