The document summarizes human reproduction and development. It describes the male and female reproductive systems and their roles in sexual reproduction and fertilization. It then outlines the key stages of human development from fertilization through birth, including embryonic development, fetal growth in the womb, and the role of the placenta during development. It concludes by explaining the three stages of childbirth.
2. Introduction
Not all animals have sexual
reproduction, but most do
Gametes are produced in the gonads-
sperm produced in testes and eggs
produced in ovaries
Zygote- the fertilized egg
3. Introduction
Many animals have external
fertilization- where each parent deposits
egg and sperm in same place,
fertilization occurs outside the body
Internal fertilization- when sperm is
introduced to female by copulation,
fertilization occurs within the body
4. Ways of Reproduction
Oviparous- lays eggs, either in water or
land
Ovoviviparous- eggs retained in body
until they hatch- give birth to living
young
Viviparous- produce living young- there
is no membrane bound egg
5. Human Reproduction
Essentially two groups of parts:
1. Gonads (testes or ovaries) that
produce the gametes and the sex
hormones
2. Accessory organs that conduct
gametes and in females house the
embryo and fetus during development
7. Male System
Testes produce sperm, are suspended in
the scrotum
Sperm production must occur at a
lower temperature than the body- that
is why they are located there
Epididymis - a coiled tube just outside
each testis, where sperm mature
8. Male System
Vas deferens- sperm move into these ducts when they
are mature, wait to move into the ejaculatory duct here
Sperm is mixed with secretions from 3 glands to
produce semen
1. Seminal vesicles- just below bladder, secrete
nutrients for the sperm
2. Prostate gland- alkaline fluid believed to
increase motility
3. Bulbourethral gland- lubricating secretions
9. Male System
After combining with seminal fluids from
various glands in the ejaculatory duct, semen
is expelled from the penis through the urethra
(which carries urine as well as semen)
During ejaculation in the male orgasm, sperm
enter the ejaculatory duct from the vas
deferentia, then muscle contractions from the
urethra and muscle at the base of the penis
eject the semen
10. Male System
Testes produce sperm
Each sperm has a
flagellum which
allows it to swim
Normal ejaculate
~40 million sperm/
mL
11. Male System
The hypothalamus controls the production
of the testes by secreting gonadotropic
secreting hormone, which triggers
1. folicle stimulating hormone-
promotes spermatogenesis
2. Leutenizing hormone- controls
production of testosterone
12. Male System
Testosterone main sex hormone in males
1. Essential for normal development
and function of sex organs
2. Necessary for maturation of sperm
3. Initiates and maintains
development of secondary sex
characteristics
14. Female System
Ovaries contain eggs
Ovum exit the ovaries and are picked up by the
oviducts/ fallopian tubes
Fertilization occurs in the first 1/3 of the
fallopian tube, then cilia and muscle
contractions move fertilized egg to the uterus
The uterus is about the size of a pear when idle.
The narrow end that meets the vagina is the cervix
15. Female System
Fertilized embryo will imbed itself in the lining
of the uterus, the endometrium
External female sexual organs are collectively
called vulva
Mons pubis, labia minora and majora, and
clitoris- homologous to penis
hymen- thin membrane which covers vaginal
opening, broken by activities of many sorts
16. Female System
Females are born with eggs, they do not make
them throughout life as males make sperm
However, development occurs:
Born with Primary oocytes (2n)
Some of these will develop into secondary
oocytes (n)
These are then released from the ovary
during ovulation
17. Female System
Estrogen- one main female sex hormone
Essential for development and function of
female sex organs
Responsible for secondary sex
characteristics
Progesterone- other main female sex hormone
Works with estrogen to control different
parts of the cycle
18. Female System
Menstrual cycle
Caused by female sex hormones cycling to cause oocyte
development and ovulation
Days 1-5- hormone levels low, menstruation occurs as
endometrium disintigrates
Days 6-13- Increased estrogen causes endometrium to
thicken
Day 14- ovulation
Days 15-28- increased progesterone causes endometrium
to double in size- it is ready to receive embryo
19. Human Development
Fertilization- when sperm and egg fuse to
form a zygote
Embryonic period- first two months
First, embryo becomes multicellular
Cleavage- lots of cell division without growth
- forms morula
Morula becomes hallow, then called blastocyst
20. Human Development
Gastrulation- 3rd week- the movement
of cells to establish the three germ layers:
endoderm, mesoderm, and ectoderm
Neurulation- formation of the central
nervous system
Form notochord from mesoderm
Form CNS from part of ectoderm
21. Human Development
At 5 weeks, limb buds appear- this will
develop into limbs
Sense organs begin to form
6-8 weeks- begins to look very human
At 8 weeks, is only 1.5 inches long,
but has all organ systems
22. Human Development
3-9 months is basically growth
Heartbeat heard around week 10
Weight increases 600 times
Length increases as well
Fetus is able to move starting around 3rd
month
Organs also continue to develop and grow
23. Placenta
The ‘sack’ that the fetus is in- has a fetal side
and a maternal side
Maternal and fetal blood do not mix;
exchange occurs across the placenta
There are chorionic villi where the exchange
occurs- lots of capillaries around them
The umbilical cord goes from the fetus to
the placenta, is part of the fetal circulation
24. Birth
Probably initiated by the fetal brain
becoming mature enough- brain then
releases hormones which are used by the
placenta to create three more hormones
estrogen, oxytoin, prostaglandin
These three hormones cause the uterus
to contract
25. Birth
Birth occurs in three basic stages:
1. Dilation of cervix, amnion breaks
(Water breaks)
2. Birth of baby
3. Delivery of placenta (afterbirth)
