IB MYP Biology

1. REPRODUCTIVE
SYSTEM

2. Objectives
• Describe the organs of the male and female human
reproductive systems

3. Guiding Question
What is reproduction?

4. The primary sex organs (gonads) are
those that produce gametes (sperm
and eggs)
Male: testes Female: ovaries

5. Sex Organs
Male:
ducts, glands, penis
Female:
uterine tubes, uterus, vagina

6. MALE ANATOMY

7. Male Secondary Characteristics
• Puberty
• Burst of hormones activate maturation of the gonads: testes
• Enlargement of the external and internal genitalia
• Voice changes
• Hair growth
• Mental changes
• Changes in body conformation and skin
• Sebaceous gland secretions thicken/increase  acne
• Begins: 9 – 14 yrs of age
• Abnormally early = precocious puberty
• Delayed = eunuchoidism

8. Timeline
Infancy
Erections begin
Ages 11-14
Secondary sex characteristics appear
Ages 13-16
Sperm produced in adult amounts (puberty)
Late teens
Peak sexual urges for boys
Throughout life
 If good health is present, there is the sex urge and ability to father
children

9. External Anatomy
Scrotum
Shaft
Foreskin
Glans
Penis

10. Penis
• It has three external parts:
• Shaft – contains the urethra – a passage for urine to
leave the body
• Glans – has opening for urethra, homologous to the
clitoris in females
• Foreskin -– a sheath of skin that covers the tip of the
penis
• It functions to both ability for urination and the transfer
sperm to the vagina.
• During sexual activity, the penis becomes erect or firm
• Ejaculation – occurs when sperm are released from the penis after
sexual excitement

11. Scrotum
• A sac-like pouch located behind the penis that holds each
testes
• Protects testes and maintain the temperature of the testes
2 degrees lower than body temperature.
• Improves sperm maturation

12. Internal Anatomy

13. Testes
• The two testes are small organs that lie in the scrotum
and produce sperm and the male hormone testosterone.
• They are the male sex gland.
• They are the counterpart to the female ovary.
• Loss of one does not impair the function of the other.
• Four to five billion sperm cells are produced each month.

14. Testosterone
• The male reproductive hormone made by the testicles
which causes the changes of puberty.
• This hormone causes secondary sex characteristics,
production of sperm and sexual urge.
• It is produced in the testicles and enters the bloodstream
at a fairly constant rate.

15. Sperm
• The microscopic cells produced by the male's testicles
which can fertilize the female's ovum.
• They are tiny, living cells 100 times smaller than a pencil
dot.
• Enough sperm would fit on the head of a pin to re-populate
the earth if each sperm fertilized an egg.
• It is destroyed by warm body temperature, acidic
environment.
• It can survive in a women’s body for 5-8 days.
• Any sperm not ejaculated are passed in the urine.

16. Epididymis & Vas Deferens
• Epididymis = maturation site for
sperm
• Vas Deferens = two long, thin tubes
that serve as a passageway for sperm
towards the urethra

17. Seminal Vesicles
• Two small glands that secrete a
sugar-rich fluid that nourishes
and enables the sperm to move.
• Makes 60% of semen volume
Prostate Gland
• The gland secretes an alkaline
fluid that neutralizes the acid
found in the male urethra and
the female reproductive tract.
• Without the fluids of the
prostate, many sperm would die
and fertilization of an egg would
be impossible.
• 40% of semen volume

18. Urethra
• A tube that both semen
and urine pass
• Semen and urine never mix.
• During urination
• one sphincter will relax so
that the bladder will push
urine out from the body.
• During ejaculation
• another sphincter will relax
so that semen can flow
through the urethra to the
outside of the body.

19. Semen, Sperm & Fertilization
• Spermatogenesis
• Development of sperm
• Major constituents of semen
• Sperm, fructose (sugar for sperm), prostaglandins (comes from the
prostate)
• Sperm are viable for 2 days (egg: 12-24 hr)
• Only ~ 100 reach the destination.
• Only one sperm fertilizes the egg.

22. 31-22
Diseases and Disorders of the Male
Reproductive System
Disease/Disorder Description
Benign prostatic
hypertrophy (BPH)
Nonmalignant enlargement of the prostate
gland; common in older men
Epididymitis Inflammation of an epididymis; usually
starts as an urinary tract infection
Impotence or
erectile dysfunction
(ED)
Disorder in which erection cannot be
achieved or maintained; about 50% of males
between 40 and 70 have some degree of ED

23. 31-23
Diseases and Disorders of the Male
Reproductive System
Disease/Disorder Description
Prostate cancer Most common form of cancer in men over
40; risks of developing it increase with age
Prostatitis Inflammation of the prostate gland; may be
acute or chronic
Testicular cancer Malignant growth in one or both testicles;
more common in males 15–30 years; more
aggressive malignancy

24. FEMALE ANATOMY

25. Female Secondary Characteristics
• Puberty
• Burst of hormones activate maturation of the gonads: ovaries
• Begins: 8-13 yrs of age
• Abnormally early = precocious puberty
• Delayed =Primary Amenorrhea
• Axillary & pubic hair growth
• Changes in body conformation [widening of hips,
development of breasts]
• Onset of first menstrual period [menarche]
• Mental changes

26. Timeline
• Ages 9-12
• Secondary sex characteristics appear
• Ages 11-14
• Menstrual cycle begins
• Late 20-30's
• Peak sexual urges
• Ages 45-55
• Menopause (cycle stops, but sex urge continues)

27. External Anatomy

28. Labia Majora & Minora
• External visible is known as the vulva (not the vagina)
• Mons pubis or "mound of Venus" is the V-shaped
area covered with hair
• Labia majora
• Rounded folds of adipose tissue and skin
• Protect other external reproductive organs
• Homologous to scrotum
• Labia minora
• Fold of skin between labia majora
• Very vascular
• Merge to form hood over clitoris

29. Clitoris & Perineum
• Clitoris
• Contains female erectile tissue
• Rich in sensory nerves
• Homologous to glans
• Perineum
• Between vagina and anus
• Area for episiotomy, if needed, during birth
process

30. Urethra & Vaginal Opening
• Urethra
• The urethra is below the clitoris is the passage for urine
• It is much shorter than the male urethra, can be more
likely to develop a UTI
• Vaginal Opening
• The entrance to the actual vagina
• It is the tube that is used for flow of menstrual fluid,
penetration during sex, and birth
• The hymen is a thin fold of tissue which partially covers
the opening of the vagina.
• Medically it is no longer considered to be a 100% proof of female
virginity.

31. Internal Anatomy

32. Ovaries
• Each ovary is about the size and shape of an almond.
• It is homologous to testes
• In young women the ovaries are about 1½ - 2 inches long,
1 inch wide & 1/3 inch thick.
• After menopause they tend to shrink.
• The female baby is born with all the ova she will ever
have (about 200,000 in each ovary).
• About 400-500 ova mature and are released over a lifetime

33. Ovaries Part II
• Ovaries have two main functions:
• store and release the ova or female egg cell. Some of
the ova disappear; others are dormant until each is
ripened and released after puberty.
• This process is called oogenesis
• produce female sex hormones estrogen and
progesterone
• They are the largest cells in the female body
(about the size of a grain of sand.)

34. Estrogen
• Estrogen is responsible for the secondary sex
characteristics and the sex drive in females.
• It spurs the onset of puberty and is responsible for ovulation
(release of a mature egg).
Progesterone
• Progesterone builds up the lining of the uterus called the
endometrium in preparation for the fertilized ovum

36. Fallopian Tubes
• Stretch from the uterus to the ovaries and measure about
8 to 13 cm in length.
• The ends of the fallopian tubes lying next to the ovaries
feather into ends called fimbria
• The fimbria (with cilia) beat in waves hundreds of times a
second catching the egg at ovulation and moving it
through the tube to the uterine cavity.
• Fertilization typically occurs in the fallopian tube

37. Uterus
• Pear-shaped muscular organ in the upper female
reproductive tract.
• It’s purpose is to provide a place for a developing embryo
• The cervix is the lower portion of the uterus that connects
with the vagina and serves as a sphincter to keep the
uterus closed during pregnancy until it is time to deliver a
baby.
• The uterus expands considerably during the reproductive
process.
• It can grow to from 10 to 20 times its normal size during pregnancy.

38. Uterus Part II
• The main body consists of a firm outer coat of muscle
(myometrium) and an inner lining of vascular, glandular
material (endometrium).
• The endometrium thickens during the menstrual cycle to
allow implantation of a fertilized egg.
• Pregnancy occurs when the fertilized egg implants
successfully into the endometrial lining. If fertilization does
not occur, the endometrium sloughs off and is expelled as
menstrual flow.

39. Vagina
• vagin = sheath
• A muscular, ridged sheath connecting the external
genitals to the uterus.
• Functions as a two-way street, accepting the penis and
sperm during intercourse and roughly nine months later,
serving as the avenue of birth through which the new
baby enters the world

40. Cervix
• The neck of the uterus.
• The cervix is lined with mucus, the quality and quantity of
which is governed by monthly fluctuations in the levels of
the estrogen and progesterone.
• When estrogen levels are low, the mucus tends to be thick and
sparse, hindering sperm from reaching the fallopian tubes.
• When estrogen levels are high (an egg is ready for fertilization) the
mucus then becomes thin and slippery, offering a “friendly
environment” to sperm.
• At the end of pregnancy, the cervix acts as the passage
through which the baby exits the uterus into the vagina.
• The cervical canal expands to roughly 50 times its normal width in
order to accommodate the passage of the baby during birth

42. Diseases and Disorders of the Female
Reproductive System
Disease/Disorder Description
Breast cancer Second leading cause of cancer deaths in
women; classified as stage 0 to 4
Cervical cancer Slow to develop; Pap smear detects
abnormal cervical cells
Cervicitis Inflammation of the cervix usually due to an
infection
Dysmenorrhea Condition with severe menstrual cramps
limiting normal activities

43. Diseases and Disorders of the Female
Reproductive System (cont.)
Disease/Disorder Description
Endometriosis Tissues of uterine lining growing outside of
the uterus
Fibrocystic breast
disease
Abnormal cystic tissue in the breast; size
varies related to menstrual cycle; common in
60% of women between 30 and 50
Fibroids Benign tumors in the uterine wall; affect
25% of women in their 30s and 40s
Ovarian cancer Considered more deadly than other types;
detection difficult and often spreads before
detection

44. Diseases and Disorders of the Female
Reproductive System (cont.)
Disease/Disorder Description
Premenstrual
syndrome (PMS)
Collection of symptoms occurring just
before a menstrual period
Vaginitis /
vulvovaginitis
Inflammation of the vagina / inflammation of
vagina and vulva; both associated with
abnormal vaginal discharge
Uterine
(endometrial) cancer
Most common in post-menopausal women;
causes about 6% of cancer deaths in women