LESSON 4: ANATOMY AND PHYSIOLOGY OF REPRODUCTION
Reproduction – process of producing off springs.
Genitals – external sex organs.
Primary sex characteristics – sex characteristics that are present at birth.
Secondary sex characteristics – sex characteristics that emerge during puberty.
Physical appearance – based on the human growth and development, the sexual
organs of men and women arise from the same structures and fulfill similar
functions.
Gonads – produces germ cells and sex hormones. Each person has a pair of gonads:
Ovaries – female gonads * the female germ cells are ova (egg)*
Testes – male gonads *the male germ cells are sperm*
THE BIOLOGICAL FEMALE
The female sexual anatomy is designed for the production and fertilization of
ovum, as well as carrying and delivering infant offspring.
A. Female external genitalia consist of the following:
Vulva – all the external genital structures taken together;
Mons veneris – pads of fatty tissue between pubic bone and skin;
Labia majora – outer lips surrounding all the other structures;
Prepuce – clitoral hood (foreskin above and covering clitoris);
Clitoris – glans (head), shaft, and crura (root), the clitoris is particularly
sensitive to stimulation;
Labia minora – inner lips surrounding the vestibule where sweat and oil
glands, extensive blood vessels, and nerve endings are located;
Vestibule – area surrounding the urethral opening and vagina, which is
highly sensitive with extensive blood vessels and nerve endings;
Urethral opening – end of tube connecting to bladder and used for
urination;
Vaginal opening – also called introitus; and
Perineum – area of skin separating the genitalia from the anus; distance
is less in females than males.
B. Female internal reproductive structures consist of the following:
Vagina – collapsible canal extending from vaginal opening back and
upward into body to cervix and uterus. During arousal, it is engorged
with blood. This aids its expansion and triggers the release of lubricants
from vaginal mucosa;
Cervix – small end of uterus to which vagina leads. It is the opening in
cervix leading to interior of uterus;
Uterus – womb, organ within pelvic zone where fetus is carried;
Fallopian tubes – carry egg cells from ovaries to uterus, this is where
fertilization occurs; and
Ovaries – produce estrogen and progesterone.
Estrogen – female sex characteristics and initiates menstrual
cycle.
Progesterone – aids in regulation of menstrual cycle and
promotes mature development of uterine lining to allow for
zygote implantation. Also produce ova, egg cells, and bring
them to maturity.
PUBERTY
- Menstrual cycle begins
- Occurs between 11 to 15 years of age.
- It may last within two to six days.
- Changes in puberty begins including: for men (growth spurt,
beard grows, voice breaks, increased body hair on limbs and
torso, pubic hair grows and genital development) and for
women (growth spurt, increased body hair on limbs and torso,
breasts form, pubic hair grows and genital development, hips
broaden, and periods start)
Menstrual phase. Occurs if the ovum is not fertilized and does not
implant itself into the uterine lining. Estrogen and progesterone levels
decrease causing the endometrium to be sloughed off and during this
time that ovarian hormones are at their lowest levels.
Proliferative phase. It occurs when the hypothalamus stimulates the
pituitary gland to release follicle-stimulating hormone (FSH) that
stimulates the ovaries to produce estrogen and causes ova to mature in
the ovarian follicles. Endometrium is repaired, thickens, and becomes
well-vascularized in response to increasing levels of estrogens.
Secretory phase. It produces progesterone and begin to secrete
nutrients, and lining becomes more vascular in response to increasing
level of progesterone.
Problem associated with menstruation include:
Premenstrual syndrome (PMS). 80-95% of women
experience.
Dysmenorrhea. Painful menstruation caused by overproduction
of prostaglandins, causing the uterine muscles to contract.
Amenorrhea. Disruption or absence of menstruation.
Menopause. Usually around age 45-50.
Female secondary sexual characteristics emerge after puberty:
1. Widening of hips and pelvis
2. Enlargement of breasts
3. Generally shorter than men
4. Greater proportion of body weight composed of fat than men
5. Two X chromosomes reduces expression of many sex-linked conditions
6. Lower mortality rate at every age and longer projected lifespan than
men.
THE BIOLOGICAL MALE
The male sexual anatomy is designed for the production and delivery of sperm
for fertilization of the female’s ovum.
A. Male external genitalia consist of the following:
Prepuce – foreskin covering head of penis, removed in male
circumcision;
Penis – glans (head), shaft, and root. During arousal, these become
engorged with blood, resulting in erection;
Corona – rim of glans where it arises from shaft;
Frenulum – thin strip of skin connecting glans and shaft on underside of
penis;
Scrotum – sac that encloses the two compartments housing the testes;
Urethral opening – found on head of penis this is the end of tube
connected to bladder and and used for urination. It is also tube to which
internal structures deliver semen by which male ejaculates; and
Perineum – area of skin separating the genitalia from the anus, distance
is greater in males than females.
B. Male internal reproductive organs:
Testes – produce androgen, particularly large quantities of testosterone,
which
Vas deferens – travels from testicle toward urethra carrying sperm;
Seminal vesicles – two glands that produces alkaline fluid rich in
fructose sugar, comprising some 70% of semen volume. Ducts carry fluid
and connect with vas deferens forming ejaculatory ducts;
Ejaculatory ducts – connect vas deferens to urethra;
Prostate – gland producing alkaline secretions that account for about
30% of semen volume. Fluid passes through a series of ducts along wall
of urethra; and
Urethra – tube within penis that carries sperm and semen the rest of the
way to the opening of the penis.
MALE CHARACTERISTICS:
Generally taller and greater proportion of body weight composed of
water;
Proportionately larger heart and lungs, presumably to handle greater
blood fluid volume;
Exposure to greater levels of testosterone resulting in heavier body and
facial hair, but also increased frequency and degree of baldness; and
Single X chromosomes resulting in sex-linked conditions such as
colorblindness and hemophilia.
MALE HORMONES
Testosterone – major male hormone produced mainly by the testes, but
there are other glands called the adrenal glands that also produce some
testosterone.
- Also responsible for the growth and development of a boy during
adolescence and for the development of sperm and secondary
characteristics.
Adrenal glands - In case a man has lost his testes, these glands would
continue to produce testosterone to support the male physical appearance.
Male secondary sexual characteristics that emerge after puberty:
No monthly cycle;
Elongation of vocal cords (lower voice);
Broader shoulders; and
Deeper chest cavity.
