
Parts to know on the
testis tissue:
› wall of seminiferous
tubule
› Fluid inside
seminiferous tubule
› Blood vessel
› Interstitial cells
(Leydig cells)
secrete testosterone

Interstitial Cells (Leydig cells): adjacent to the
seminiferous tubules in the testicle. They can secrete
testosterone and are often closely related to nerves.
Leydig cells have round vesicular nuclei and an
eosinophilic cytoplasm
› Leydig cells release a class of hormones called androgens.
They secrete testosterone, androstenedione and
dehydroepiandrosterone (DHEA), when stimulated by the
pituitary hormone LH. LH increases cholesterol desmolase
activity, leading to testosterone synthesis secretion by Leydig
cells.
› FSH increases the response of Leydig cells to LH by increasing
the number of LH receptors expressed on Leydig cells.

Germinal epithelium (male): innermost layer of the testicle
› cellular covering of internal and external surfaces of the body,
including the lining of vessels and other small cavities. It consists
of cells joined by small amounts of cementing substances
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Developing cells: are able to revert back into an embryoniclike stem cell state, which could then be driven into chosen
cell types; can continue to produce sperm
› In science today, testis tissues have been found to be
“stem-like” cells that are capable of being harvested and
used in the future
developing spermatozoa: aka sperm
› Spermatogenesis is the production of spermatozoa and
occurs in the narrow tubes called seminiferous tubules in
the testes
Sertoli cells: a 'nurse' cell of the testes which is part of a
seminiferous tubules; nurtures developing sperm cells through
spermatogenesis
› It is activated by FSH and has FSH receptors on its
membranes.

6 Stages total:
› 1. An outer layer called the germinal epithelium cells [2n]
›
›
›
›
›
divide endlessly by MITOSIS to produce more diploid cells
2. Diploid cells GROW larger and are then called primary
spematocytes [2n]
3. Each primary spermatocyte carries out the FIRST
DIVISION OF MEIOSIS to produce two secondary
spermatocytes [n]
4. Each secondary spermtocyte carries out the SECOND
DIVISION OF MEIOSIS to produce two spermatids [n]
5. Spermatids become associated with nurse cells, sertoli
cells, which help the spermatids to develop into
spermatozoa [n]. This is CELL DIFFERENTIATION.
6. Sperm detach from sertoli cells and eventually are
carried out of the testis by the fluid in the centre of the
seminiferous tubule.
Hormone
Source
Role
FSH
Pituitary Glands
Stimulates primary
spermatocytes to
undergo the first
division of meiosis, to
form the secondary
spermatocytes
Testosterone
Interstitial cells in the
tubules
Stimulates the
development of
secondary
spermatocytes into
mature sperm
LH
Pituitary Glands
Stimulates the
secretion of
testosterone by the
testis

Parts to know on the
ovary:
› Region where blood
›
›
›
›
vessels enter and
leave
Outer layer of
germinal epithelium
cells
Cortex [containing
primary follicles]
Secondary oocyte
inside a mature follicle
Medulla [containing
blood vessels]

Germinal Epithelium: surface of the ovary covered by
a layer of simple cuboidal cells
› These cells are derived from the mesoderm during
embryonic development and are closely related to the
mesothelium of the peritoneum. The germinal epithelium
gives the ovary a dull gray color as compared with the
shining smoothness of the peritoneum; and the transition
between the mesothelium of the peritoneum and the
columnar cells which cover the ovary is usually marked by
a line around the anterior border of the ovary.
› The germinal epithelium gives rise to primary follicles

Primary Follicles: Located inside the cortex; develop
receptors to FSH at this time, but they are
gonadotropin-independent up until the latter stages
Mature Follicle: contains secondary oocyte; bursts
open and releases the egg with increased levels of
LH, starting ovulation
 Secondary Oocyte: An oocyte in which the first
meiotic division is completed. The second meiotic
division usually stops short of completion unless
fertilization occurs; b/w first and second maturation
development


8 STEPS:
›
›
›
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›
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1. In the ovaries of a female fetus, germinal epithelium cells [2n] divide by
MITOSIS to form more diploid cells [2n]
2. Diploid cells GROW into larger cells called primary oocytes [2n]
3. Primary oocytes start the FIRST DIVISION OF MEIOSIS but stop during the
prophase I. The primary oocyte and a single layer of follicle cells around
forma primary follicle
4. When a baby girl is born the ovaries contain about 400,000 primary follicles
5. Every menstrual cycle a few primary follicles start to develop. The primary
oocyte completes the first division of meiosis, forming two haploid nuclei. The
cytoplasm of the primary oocyte is DIVIDED UNEQUALLY forming a large
secondary oocyte [n] and a small polar cell [n]
6. The secondary oocyte starts the SECOND DIVISION OF MEIOSIS but stops in
prophase II. The follicle cells meanwhile are proliferating and follicular fluid is
forming.
7. When the mature follicle bursts, at the time of ovulation, the egg that is
released is actually still a secondary oocyte.
8. After fertilization the secondary oocyte completes the second division of
meiosis to form an ovum, [with a sperm nucleus already inside it] and a
second polar cell or body. The first and second polar bodies do not develop
and eventually DEGENERATE.
FEATURES TO LABEL: HEAD, ACROSOME, HAPLOID NUCLEUS, MID-PIECE, TAIL, PROTEIN
FIBERS TO STRENGTHEN TAIL, MICROTUBULES IN A 9+2 ARRANGEMENT, HELICAL
MITOCHONDRIA, CENTRIOLE, PLASMA MEMBRANE
FEATURES TO LABEL: TWO CENTRIOLES, FIRST POLAR CELL, PLASMA MEMBRANE,
LAYER OF FOLLICLE CELLS [CORONA RADIATA], LAYER OF GEL COMPASED OF
GLYCOPROTEINS [ZONA PELLLUCIDA], CORTICAL GRANULES, CYTOPLASM/YOLK
CONTAINING DROPLETS OF FAT, HAPLOID NUCLEUS

The three main structures: Epididymis, Seminal vesicles, and
Prostate gland
› When sperm first arrive in the epididymis from the testes,
they are unable to swim
› While in epididymis, sperm matures and learn to swim
› The prostate gland and two seminal vesicles produce and
store fluids that are later expelled during ejaculation
› The fluid them mixes with them sperm and increased the
volume of the ejaculate
 The fluid from the seminal vesicle contains nutrients, like
fructose, for the sperm and a muscus to protect it in the
vagina
 The fluid from the prostate gland has mineral ions and
protects the sperm from the vagina’s acidic conditions
due to its alkalinity.
Similarities:
› Both start with the proliferation of cells by mitosis
› Both involve the cell growth before mitosis
› Both involve the two divisions of meiosis
 Differences:

Spermatogenesis
Oogenesis
Millions produced daily
One produced every 28 days
Released during ejaculation
Released on about day 14 of menstrual cycle
by ovulation
Sperm formation starts during puberty in boys
The early stages of egg production happen
during fetal development in females
Sperm production continues throughout the
adult life of men
Egg production becomes irregular and then
stops at the menopause in women
Four sperm are produced per meiosis
Only one egg is produced per meiosis

6 steps total:
› 1. Arrival of sperm: Sperm attracted by a chemical
signal and swim up the oviducts to reach the egg.
Fertilization is only successful if many sperm reach the
egg {sperm tries to push through the layers of follicle
cells around the egg}
› 2. Binding: The 1st sperm to break through the layers
of follicle cells binds to the zona pellucida. This
triggers the acrosome reaction.
› 3. Acrosome Reaction: The contents of the acrosome
are released by the separation of the acrosomal cap
from the sperm. Proteases from the acrosome digest
a route for the sperm through the zona pellucida,
allowing the sperm to reach the plasma membrane
of the egg

Fertilization continued
› 4. Fusion: The plasma membrane of the sperm and egg
fuse and the sperm nucleus enters the egg and joins the
egg nucleus. Fusion causes the cortical reaction.
› 5. Cortical Reaction: Small vesicles called cortical granules
move to the plasma membrane of the egg and fuse with
it, releasing their contents by exocytosis. Enzymes from the
cortical granules cause the cross linking glycoproteins in
the zona pellucida, making it hard and preventing the
entry of anymore sperm
› 6. Mitosis: The nuclei from the sperm and the egg do not
fuse together. Instead, both nuclei carry out mitosis using
the same centrioles and spindle of microtubules. A 2celled embryo is produced

HCG: human chronic gonadotrophin; prevents
degeneration of the corpus luteum.
› Estrogen and progesterone are needed throughout
pregnancy to stimulate the development of the uterus
lining. During the first few days after ovulation, the corpus
luteum secretes these hormones whether or not there has
been fertilization. After implanting in the uterus wall, the
embryo starts to secrete HCG.
› HCG stimulates the corpus luteum to grow and to
continue secretion of estrogen and progesterone. This is
essential to allow the pregnancy to continue.
› By the middle of the pregnancy, the corpus luteum starts
to degenerate, but by then the cells in the placenta are
secreting estrogen and progesterone and these cells
secrete increasing amounts until the end of the
pregnancy.

Fertilization: Fusion of the egg and the sperm
› During copulation, or sexual intercourse, semen is
ejaculated into the vagina. Sperm swim through the
cervix, up the uterus and into the oviducts. If there is
an egg in the oviducts, the sperm can fuse with it to
produce a zygote

Zygotes produced in the oviduct = new
individual
› Zygote starts to divide by mitosis and forms a 2-cell
embryo, and then a 4-cell embryo and so on until a
blastocyst, or a hollow ball of cells, is formed
› During these stages embryo is transported down the
oviducts to the uterus {at about 7 days old the
embryo implants itself into the wall of the uterus to
continue development}.

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Placenta: a disc-shaped structure, 185 mm in diameter and 20
mm thick when fully grown.
Placentile Villi: small projections that give a large surface area,
14 m^2, for gas exchange and exchange of other materials.
Fetal blood flows through the capillaries in the villi
Inter-villous Spaces: Maternal blood flows through these spaces,
brought by the uterine arteries and carried away by the uterine
veins.
Myometrium: muscular wall of the uterus used during childbirth.
Oxygenated Fetal Blood: flows back to the fetus from the
placenta along the umbilical vein
De-oxygenated Fetal Blood: flows from the fetus to the placenta
along the umbilical arteries
Endometrium: the lining of the uterus which the placenta grows
The fetus develops an amniotic sac
containing amniotic fluid around it.
 The fetus floats in and is supported by the
amniotic fluid b/c the fluid acts as a
shock absorber (such as everyday
events, or accidents that impacts the
mother’s abdomen)


Background Info
› 8 weeks+, embryo starts to develop tissue,
becoming a “fetus.” The placenta and umbilical
also develop.
 The placenta has many projections called
placenta villi embedded in the uterine wall.
 In the placenta, the blood of the fetus flows close
to the blood of the mother in the uterus wall.
› Materials are exchanged between the maternal
and fetal blood
 Ex: Oxygen passes from maternal to fetal blood
and Carbon Dioxide passes from fetal to maternal
blood

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

Over 9 months of pregnancy, progesterone
ensure that the uterus develops and sustains
the growing fetus
Levels are increasingly high until end of
pregnancy in which a rapid decrease of the
hormone occurs.
This causes secretion of oxytocin which causes
the muscles of the uterus wall to contract
The uterine contractions then become stronger
and stronger due to increase of oxytocin,
creating a positive feedback
 John Jacob Jingle Heimer Schmitt, his name was my name,
too!