Reproduction and Development

Question 1

Structures of the human female reproductive system

Answer 1

Ovaries: produces eggs and sex hormones

Fimbriae: sweep an egg into an oviduct

Oviducts: conduct an egg from ovarie to uterus

Uterus: houses the developing fetus

Cervix: is the opening to the uterus

Vagina: recieves the penis during sexual intercourse

Question 2

Structure of the human male reproductive system

Answer 2

Testes: produces sperm and sex chromosomes

Epididymides: mature and store developing sperm

Ductus deferentia: conduct and store sperm

Seminal vesicle: contribute fructose and fluid to semen

Prostate gland: contributes alkaline and mucoid fluids to semen

Urethra: conducts semen trough penis

Penis: carries semen into female reproductive tract

Question 3

Sperm

Answer 3

Tadpole – shaped
Has three parts: oval head, cylindrical middle,
tail
The head contains the chromosomes and is
covered by a cap-like structure called the
acrosome
The acrosome stores enzymes needed to get into
the egg
Middle contains mitochondria to provide energy
Tail provides movement (a speedy 3mm/hr)

Question 4

Ovum

Answer 4

A mature ovum is a non-motile, sphere-shaped
cell (20x larger than sperm)
Contains a large quantity of cytoplasm that
contain nutrients for the first days of
development after fertilization
Encased in a thick membrane
Can survive in the oviduct for
up to 24 hours after ovulation

Question 5

Chromosomal factors

Answer 5

The chromosomal sex (genetic sex) of an
individual is determined at fertilization
Females: XX (one from father, one from mother)
Males: XY (X from mother, Y from father)
Male gametes determine the sex of the
individual

Until the 7th week of development male and
female embryo’s are identical
After this time the presence or absence of
specific hormones determines which sex organs
develop

Question 6

Hormones

Answer 6

Question 7

Clevage implantation

Answer 7

Within 30 hours of being fertilized
the zygote divides into 4 cells, 8
cells, 12 cells, etc.
The zygote does not get any bigger –
the cells get smaller
This process of cell division without
enlargement is known as cleavage

The zygote will reach the uterus within 3-5
days after fertilization
Begins to fill with fluid diffused from the
uterus and is now called a blastocyst
The blastocyst has 2 components:
The outer layer is the trophoblast which
will develop into a membrane called the
chorion which becomes the placenta
the placenta provides nutrient and oxygen
to the fetus and removes waste
The other section forms within the
blastocyst to form the inner cell mass
The inner cell mass develops into the
embryo

Between the 5th and 7th day after
fertilization the blastocyst attaches to
the endometrium = implantation
Completed by the 10th – 14th day

When implantation begins the trophoblast
starts to secrete human chorionic
gonadotropin hormone (hCG)
hCG has the same effects as LH so will
maintain the corpus luteum

As a result estrogen and
progesterone are still secreted
hCG will continue to be secreted for
about 4 months

Question 8

Primary germ layres

Answer 8

1. Ectoderm – outer layer
2. Mesoderm – middle layer
3. Endoderm – inner layer

These layers will make all the future
tissues, organs and organ systems
of the body

Gastrulation marks the start of
morphogenesis
Morphogenesis is a series of events
that form distinct structures of the
organism - Makes the different cells of the body
(differentiation

Question 9

Neurolation and organ formation

Answer 9

Between the 3rd and 8th weeks the
organs form
3rd week – band of mesoderm cells
start forming a backbone
The nervous system forms from the
ectoderm

Neurulation – process of forming
the neural tube which will become
the brain and spinal cord; marks the
start of organ formation
By 18th day the heart starts beating

4th week – rapid growth, blood cells
start to form and fill blood vessels,
lungs and kidneys take shape, head
is visible, arm and leg buds are
visible

5th week – head is very large, eyes
open (no iris or eyelids)
6th week – brain continues
development, limbs lengthen, gonads
start producing hormones

7th & 8th weeks – distinct human
characteristics, organs are formed,
eyes are well developed, nostrils are
developed

By eight weeks the embryo is the
size and mass of a paper clip but has
approximately 90% of all of its
organs