SEXUAL REPRODUCTION AND DEVELOPMENT

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SEXUAL REPRODUCTION AND DEVELOPMENT
SEXUAL REPRODUCTION
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SEXUAL REPRODUCTION
Sexual reproduction requires two different parent
cells from two separate organisms or from two
sexually different parts of a single organism.
Sexual reproduction produces off springs that
are genetically different from either parent. In
simple organisms, sexual reproduction involves
transport of genetic material from one organism
to another. In more complex organisms, two
special sex cells, called gametes are needed.
(pg 417)
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TYPES OF GAMETES
l) ISOGAMY
It is a condition in which the sexual cells
(gametes) are of the same form and size. Many
algae and some fungi have isogamous gametes. Ex
Ulotrix
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TYPES OF GAMETES
ll) HETEROGAMY
It is a condition of having differently sized
male and female gametes.
A) ANISOGAMY
The union of morphologically unlike motile
gametes.
Oedogonium sp. (green algae)
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TYPES OF GAMETES
B) OOGAMY
The union of unlike gametes, usually a large
non-motile female gamete and a small motile male
gamete.
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A) Conjugation
EXCEPTIONAL CASES IN SEXUAL REPRODUCTION
The type of sexual process most commonly found
among simple organisms is called conjugation. In
conjugation, a cytoplasmic bridge forms between
two cells, and an exchange or transfer of nuclear
material takes place through the bridge. Ex
Paramecium, bacteria
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B) Hermaphroditism
EXCEPTIONAL CASES IN SEXUAL REPRODUCTION
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B) Hermaphroditism
In some animals sexes are not separate. Instead,
each individual has both testes and ovaries.
These organisms are called hermaphrodite.
Hermaphroditism is usually found among animals
that move slowly or those that are attached to
surface. Ex earthworms, flatworms, snails,
hydras, sponges and some flowering plants.
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B) Hermaphroditism
Even though hermaphroditic organisms can produce
both eggs and sperm, self-fertilization is rare.
Instead, these organisms exchange sperm with
another individual of the same species.

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B) Hermaphroditism
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Self fertilization is seen in flatworms but not
in earth worms.
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Reproductive organs of sponges are not found at a
particular site of the organism. Some cells found
in different places of the organism produce eggs
and sperms.
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C) Parthenogenesis
mitosis
worker (2n) Sterile female
honey
Male bee(n)
Sperm cells (n)
fertilization
royal jelly
(2n) female
Queen (2n)
meiosis
Egg cells (n)
Queen (2n)
meiosis
No fertilization
Drone (n)
parthenogenesis
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C) Parthenogenesis
The development of an unfertilized egg into adult
animal without fusion with sperm is called
parthenogenesis. In nature it takes place in
many insects, including bees, wasps and certain
ants. For example, in bees, the queen bee mates
only once. She can then produce either
unfertilized eggs or fertilized eggs. The
unfertilized eggs become male drones while the
fertilized eggs become female workers or queen.

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SEXUAL REPRODUCTION IN ANIMALS
External Fertilization
Internal Fertilization
The gametes fuse outside of the body
The gametes fuse inside the body of female
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EXTERNAL FERTILIZATION
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EXTERNAL FERTILIZATION

• In external fertilization, the eggs are in the
  environment outside the body of the
• female.
• Takes place in animals that live in water.
• Ex Fish (but not sharks), many amphibians
• To overcome the hazards of external
  fertilization, large numbers of eggs and sperm
  are released.
• Embryo inside the fertilized egg develops in
  aquatic environment.

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EXTERNAL FERTILIZATION
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INTERNAL FERTILIZATION
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INTERNAL FERTILIZATION
Fertilization within the body of the female is
called internal fertilization. It is found most
often in animals that reproduce on land and also
found in some aquatic animals, such as sharks.
Internal fertilization requires a specialized
sex organ to carry sperm from the body of the
male into the body of the female. Less number of
eggs are produced After fertilization, either
the zygote is enclosed in a protective shell and
released by the female, or it remains and
develops within a special part of the females
body.
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Metamorphosis
In some animals that produce large number of
eggs, embryo hatches into nymph or larvae before
it completes its development. Nymphs or larvae
complete their development at the outside and
become adults. This series of changes is called
metamorphosis.
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Metamorphosis
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REPRODUCTION IN FISH AND AMPHIBIANS

• Eggs are not covered with a hard shell, instead
  they are surrounded by a jellylike substance.
• Eggs that are produced in the ovaries of females
  pass to the Müllers duct through the
• ciliated funnel (kirpikli huni) and then
  released out of the body from the cloaca (kloak).
  
• Wolfs duct carries both sperms and excretory
  materials to the cloaca in males.

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REPRODUCTION IN FISH AND AMPHIBIANS
Egg
Kidney
Testes
Ciliated funnel
Mullers duct
Ovary

Kidney
Wolfs duct
Urinary bladder
Ureter
Urinary bladder
Cloaca
Cloaca
Male fish and amphibian urogenital system
Female fish and amphibian urogenital system
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REPRODUCTION IN REPTILES AND BIRDS

• Internal fertilization is mostly seen in
  reptiles and birds.
• Embryo found in the fertilized egg completes its
  development inside the egg.
• In females, eggs are transferred to the cloaca
  through the Mullers duct. Inside the Mullers
  duct egg white and shell are formed.
• Wolfs duct carries only sperms in males. Egg
  shells of birds are harder than reptiles.
  Fertilization occurs in Mullers duct.
• Excretory substances are transported from a
  separate duct to the cloaca.

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REPRODUCTION IN REPTILES AND BIRDS
Testes
Ovary
Ciliated funnel
Mullers duct
Wolfs duct
Kidney
Egg
Ureter
Ureter
Urinary bladder
Urinary bladder
Cloaca
Cloaca
Female Reptile and Bird Urogenital system
Male Reptile and Bird Urogenital system
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Bird Reproductive System
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• After fertilization, the development of chordates
  can be
• oviparous, ovoviviparous or viviparous.
• In oviparous species, which include most fishes
  and amphibians and all birds, the eggs develop
  outside the mothers body. Embryo obtains
  nutrients from the egg.

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In ovoviviparous animals, such as sharks, the
eggs develop within the mothers body and the
embryos receive nutrients from the yolk in the
egg.
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The developing embryos of viviparous animals,
including most mammals, obtain nutrients directly
from the mothers body.
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EXTRAEMBRYONIC MEMBRANES IN REPTILES AND BIRDS

• Embryonic membranes formed during the
  development of reptiles and birds are
• Chorion (serosa)
• Allantois
• Amnion
• Yolk sac (Vitellus sac)

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EXTRAEMBRYONIC MEMBRANES IN REPTILES AND BIRDS

• CHORION The outermost membrane lines the inside
  of the shell and surrounds the embryo and other
  three membranes.
• It aids in the exchange of gases between the
  embryo and the environment.
• In mammals, chorion is involved in the
  formation of placenta.

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EXTRAEMBRYONIC MEMBRANES IN REPTILES AND BIRDS

• 2. ALLANTOIS is a saclike structure that grows
  out of the digestive tract of the embryo. So that
  it aids in the exchange of gases and collection
  of waste materials.
• In mammals, waste materials pass from embryo
  to the mother, therefore allantois is
  degenerated. (körelmistir)

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EXTRAEMBRYONIC MEMBRANES IN REPTILES AND BIRDS

• 3. AMNION The amniotic fluid within the sac acts
  as a cushion to protect it from shocks.
• During developmental stages of fish and
  frogs, amnion sac is not formed.
• In mammals, amnion sac is involved in the
  formation of umbilical cord (göbek bagi).

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EXTRAEMBRYONIC MEMBRANES IN REPTILES AND BIRDS
EMBRIYO ZARLARI

• 4. YOLK SAC (VITELLUS SAC)
• It surrounds the yolk (vitellus) and it is the
  source of food for the embryo.
• Yolk sac of birds and reptiles are larger
  than fish and frogs.
• As there is little amount of vitellus in the
  eggs of mammals, yolk sac is not developed as
  much. The mother meets the needs of the embryo.

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REPRODUCTION IN MAMMALS
NONPLACENTAL MAMMALS
Pouched mammals (Marsupials) (Keseli memelilerde)
Some internal development of the embryo takes
place in the uterus, but no placenta is formed.
The young animal crawls into a pouch on the
outside of the mothers body after birth and
attaches itself to a mammary gland. Development
is completed in the pouch. Ex kangaroo, opossum
(keseli ayi)
Egg-laying mammals Gagali memelilerde
(platypus, ornithorenk) The egg of egg-laying
mammals contain a large amount of yolk. The
embryo completes its development outside the body
of the mother and feeds upon the mothers milk.

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Pouched mammals
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Egg-laying mammals
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REPRODUCTION IN MAMMALS
PLACENTAL MAMMALS

• Most mammals, including humans, are placental
  mammals. (Ex hedgehog (kirpi), bat, whale,
  horse, donkey, elephant, seal, sheep)
• In these mammals, the blood vessels of the
  embryos circulatory system are in close contact
  with the mothers circulatory system. This
  contact takes place in a specialized structure
  called the placenta.
• The placenta allows the exchange of nutrients
  and wastes between the embryo and the mother.

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• In humans, the chorion is the outermost
  extraembryonic membranes.
• Small fingerlike projections called chorionic
  villi form on the outer surface of the chorion
  and extend into the uterine lining.

( Chorionic Villus uterus wall Placenta)
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In the human, the yolk sac and the allantois
develop into the umbilical cord. This rope like
structure connects the developing fetus to the
placenta. This structure contains blood vessels
that transport waste materials out of the
embryos body. Veins inside the umbilical cord
carry oxygen and nutrients to the
embryo. (Umbilical cord vitellus sac
allantois)

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THE MALE REPRODUCTIVE SYSTEM
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SPERMATOGENESIS
Is the production of sperm in testes by meiotic
division from immature sex cells called
spermatogonia (2n). In humans, after a male
matures sexually , there is a continual
development of some spermatogonia into functional
sperm.
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1. Spermatogonium increases in size to become a
primary spermatocyte. 2. The primary
spermatocyte undergoes the first meiotic
division, forming secondary spermatocytes. 3.
Each secondary spermatocyte undergoes second
meiotic division, forming 4 haploid spermatids.
4. Each of the spermatids develops into a mature
sperm with flagellum inside the epididimys.
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THE MALE REPRODUCTIVE SYSTEM

• The male gonads are testes. The testes make sperm
  cells, and the male sex hormone testosterone.
• Testosterone causes development of the secondary
  sex characters, such as, body hair, muscle
  development and a deep voices.
• Secondary sex characteristics develop during
  adolescence and are not involved in reproduction.
  

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THE MALE REPRODUCTIVE SYSTEM

• Each testis is made up of coiled tubes called
  seminiferious tubules. (300-600 tubules in each
  testis)
• Immature sperm are made in these tubes and then
  pass to the epididymis, a storage area on the
  upper rear part of each testis.
• In the epididymis, the sperm mature and leave
  through the vas deferens, a tube that leads
  upward from each testis.
• The two vas deferens empty into the urethra.
  Urethra is both the passageway for sperm and the
  excretion of urine.

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THE MALE REPRODUCTIVE SYSTEM

• In human male, urethra passes through the penis
  to the outside of the body.
• As sperm enter the urethra, the
• seminal vesicles, Cowpers gland and prostate
  gland all secrete seminal fluid into the urethra.
• The mixture of sperm and fluid is called semen.

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HORMONAL CONTROL OF THE MALE REPRODUCTIVE SYSTEM

• FSH (Follicle-stimulating hormone) In males it
  controls the production of sperm cells in testes
  by stimulating the seminiferious tubules.
• LH (Luteinizing hormone) It stimulates the
  testes and makes them secrete testosterone
• FSH, LH are secreted from pituitary gland
  (hipofiz) and testosteron is secreted from
  testes.

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FEMALE REPRODUCTIVE SYSTEM
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OOGENESIS

• Oogenesis is the production of eggs in the ovary.
  
• Eggs develop in the ovary from immature cells
  called oogonia (2n) (singoogonium).
• Oogonium is surrounded by a follicle, a sac of
  cells within which the mature egg develops.
• During the early development of the female, the
  oogonia divide many times by mitosis to form a
  supply of oogonia.
• Each human female is born with all the oogonia
  she will ever have.

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OOGENESIS

• Before birth and by the third month of
  development of a human female, oogonia within the
  babys ovaries begin to develop into cells called
  primary oocytes.
• Meiosis stops at that point until the female
  reaches to sexual maturity. Then, once a month in
  women, one of these primary oocytes finishes
  meiosis and develops into an egg.

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OOGENESIS
When the first meiotic division takes place in
the primary oocyte, the cytoplasm of the cell
divides unequally. One of the daughter cells is
large and called secondary oocyte (n). The other
small daughter cell is called first polar body
(n). (l. kutup hücresi) During the second meiotic
division, the secondary oocyte divides unequally
into a large cell called ootid and another polar
body. The first polar body also divides into two
polar bodies. (ll. kutup hücresi) The ootid grows
into a mature egg(n). The polar bodies break
apart and die.
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COMPARISON OF EGG AND SPERM

• SPERM
• is made up of head,a middle piece and flagellum
• head contains nucleus and acrosome that contains
  enzymes to make sperm penetrate the egg
• Middle piece contains mitochondria

• EGG
• Round and unable to move
• Contains nucleus and stored food in the form of
  yolk
• Larger than sperm

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THE FEMALE REPRODUCTIVE SYSTEM

• The female gonads are the ovaries. The ovaries
  makes eggs and secrete the female sex hormone
  estrogen.
• Estrogen causes the development of female
  secondary sex characteristics such as breasts, a
  broadened pelvis, and distribution of body fat.
• Estrogen plays an important role in menstrual
  cycle.

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THE FEMALE REPRODUCTIVE SYSTEM

• There are two ovaries.
• Each ovary contains about 200.000 tiny egg sacs
  called follicles.
• In each follicle, there is an immature egg.
• When an egg matures, its follicle moves to the
  surface of the ovary.

• The follicle than breaks, releasing the egg. This
  process is called ovulation.

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THE FEMALE REPRODUCTIVE SYSTEM

• Near each ovary, but not connected to it, is an
  oviduct or Fallopian tube with a funnel-like
  opening.
• Cilia lining the oviduct, transports the released
  egg into the tube. In the oviduct, the egg may
  be fertilized if any sperm are peresent.

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THE FEMALE REPRODUCTIVE SYSTEM

• From the oviduct, egg passes into the uterus.
• If the egg has been fertilized, it finishes its
  development in th uterus attached to its wall.
• The neck of the uterus is called cervix and it
  opens into the vagina (birth canal), which leads
  to the outside of the body.

• Unlike the male, in the mature female, the
  urinary and reproductive tarcts are
  completely separete.

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MENSTRUAL CYCLE
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• In human female, a mature egg develops and leaves
  one of the ovaries about every 28 days.
• At this time uterus wall thickens and is prepared
  to accept a fertilized egg.
• If the egg is not fertilized, the uterine wall
  breaks down and along with the unfertilized egg
  passes from the body.
• Then another egg matures and uterine wall builds
  up again.
• This cycle is called menstrual cycle.

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STAGES OF MENSTRUAL CYCLE

• FOLLICLE STAGE
• The pituitary gland secretes FSH (Follicle
  stimulating hormone), which causes several
  follicles in the ovary to begin developing.
• Usually one follicle matures. As the follicle
  develops, it secretes estrogen.
• The estrogen stimulates the uterine lining to
  thicken with mucus to prepare for pregnancy.
• This stage lasts 10 to14 days.

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STAGES OF MENSTRUAL CYCLE

• 2. OVULATION
• A high level of estrogen in the blood causes the
  pituitary to decrease the secretion of FSH and
  begin the secretion of luteinizing hormone (LH).
• When the concentration of LH reaches a certain
  level, ovulation takes place.
• The follicle breaks and releases the mature
  egg.

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STAGES OF MENSTRUAL CYCLE

• 3. CORPUS LUTEUM
• After ovulation, LH causes the broken follicle
  to fill with cells, forming a yellow body called
  the corpus luteum.
• The corpus luteum begins to secrete
  progesterone, which brings about the continued
  growth of the uterine lining.
• Progesterone also stops the development of new
  follicles in the ovary by inhibiting the release
  of FSH. Fertilized egg attaches to the wall of
  uterus by progesterone hormone.
• The corpus luteum stage lasts 10 to 14 days.

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STAGES OF MENSTRUAL CYCLE

• 4. MENSTRUATION
• If fertilization does not occur, secretion of
  LH decreases, and the corpus luteum breaks down.
  This causes a decrease in the level of
  progesterone.
• As the progesterone level decreases, uterine
  wall breaks down. Layers of wall, unfertilized
  egg, and small amount of blood pass out of the
  body. This is called menstruation.
• It lasts about 3-5 days.
• During menstruation, estrogen level decreases.
• The pituitary secretes more FSH and a new
  follicle starts to mature.

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HORMONAL CONTROL OF THE MALE REPRODUCTIVE SYSTEM

• Hormones produced by hypothalamus called
  releasing factors (RF), control the release of
  hormones from the pituitary gland.
• Pituitary gland secretes
• FSH (follicle stimulating hormone)
• Luteinizing hormone (LH)
• Luteotrophic hormone (prolactin)
• Secretions of pituitary effects directly the
  ovary and ovary stimulates uterus activities.

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• Luteotrophic hormone (Prolactin)
• It maintains the continuity of corpus luteum,
  and the secretion of progesterone and estrogen.
• It stimulates the secretion of milk by the
  mammary glands of the female after she gives
  birth. It is also known as prolactin.

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• During pregnancy, placenta secretes a hormone
  which acts like estrogen and progesterone and
  corpus luteum continues the secretion of
  progesterone.
• During pregnancy, progesterone helps uterine
  activities continue until the childbirth. After
  birth, placenta passes out of the body and
  secretion of progesterone stops. Thus, uterine
  walls break down and return to its position
  before birth.

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• OXYTOCIN
• It is secreted from the pituitary gland, and
  stimulates contractions of the uterus muscles
  during childbirth along with the estrogen.
• After childbirth, it helps milk that is secreted
  from the mammary glands of the female, fill the
  milk channels.

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PITUITARY GLAND HORMONES HORMONES SECRETED FROM OVARIES
FSH stimulates the development of egg cells in follicles LH causes the release of egg cells from ovaries of female (ovulation ) After ovulation, it causes the broken follicle to form corpus luteum. LTH it maintains the continuity of corpus luteum. Also stimulates the secretion of milk ESTROGEN Stimulates the development of female rep. system and secondary sex characteristics It increases the no. of ciliated epithelium cells in fallopian tubules 3. Increases the amount of blood and tissue fluid in uterus PROGESTRON It stimulates the development of uterus It increases the amount of glycogen and fat inside the fallopian tubule It helps embryo attach to the wall of uterus
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PITUITARY GLAND HORMONES HORMONES SECRETED FROM TESTES
FSH controls the production of sperm LH It stimulates testes to secrete testosteron TESTOSTERON 1.Stimulates development of male rep. system and secondary sex characteristics 2. Stimulates development of sperms