Download Biology 11 - Human Anatomy

Anatomy & Physiology Lecture
Embryology
I.
Overview
A. Fertilization
B. Preembryonic Period
C. Embryonic Period
II. Fertilization (_________________) - the penetration of an ovum by a sperm with the
subsequent union of their genetic material. This includes the following events.
A. A woman usually ovulates one _____ per month
1. The ovum is surrounded by a “________ _________” consisting of an inner zona
pellucida & outer corona radiata
2.
These layers ___________ the ovum as it enters the uterine tube
B. During coitus, a male ejaculates bet. 100-500________________ sperm into the female’s
vagina
1.
2.
Only about ____ sperm will live to encounter the ovum
3.
When a sperm penetrates the zona pellucida, the ovum forms a ______________
________________ that blocks other sperm
4.
With the sperm’s entry, the ovum completes meiosis II, and the haploid sperm and
egg nuclei unite to form a diploid _________
The head of each sperm is capped with an ________________, which contains
digestive enzymes that allow the sperm to digest the outer jelly coat of the egg
C. __________________ development can be divided into 3 periods:
1. ___________________ - first 2 weeks; initiated by fertilization
2. ___________ – weeks 3-8, in which the body organs are formed
3. ___________ - from 2 months to parturition (childbirth)
D. _____________________ includes all of the above developmental periods (conception to
birth). In humans it’s about 280 days.
III. ________________________ Period
A. Cleavage & Formation of the ______________
1.
Within 30 hrs after fertilization, the zygote undergoes mitotic cell divisions without
growth, called _____________
2.
3.
When it is a solid ball of 16 cells, it is called a _____________
The cells continue to divide and become a hollow, fluid-filled ball of cells called a
________________
a. The outer layer of cells are the __________________, which will become the
chorion, and later the embryonic placenta
b.
An inner layer of cells is the _________________________, which will become
the embryo
B. _____________________ in the uterine lining begins between the 5th & 7th day after
fertilization
1.
The blastocyst embeds itself in the ____________________
2
2.
The ______________________ secretes enzymes that digest a portion of the
endometrium
3.
4.
5.
Endometrial cells cover the embedded _________________
6.
HCG production declines by the 10th week when the developing ________________
begins to produce estrogen & progesterone to maintain the endometrium
Fingerlike ___________________ extend from the trophoblast into the endometrium
Human chorionic gonadotropin (______) secreted by the trophoblast maintains the
corpus _____________ so it continues to produce progesterone to maintain the
endometrium
C. Formation of the 3 _________ Layers begins during the 3rd week
1. An _______________ cavity forms between the inner cell mass & trophoblast
2. The inner cell mass flattens into an ______________________ and forms 3 germ
layers:
a.
b.
c.
The upper _________derm, near the amniotic cavity
The lower _________derm, near the blastocyst cavity
Later, the ______derm forms between ectoderm & endoderm
IV. ___________________ Period
A. During the embryonic period (______ wk), ______ of the body tissues & organs form,
as well as the placenta, umbilical cord, & extraembryonic membranes
B. __________ layers differentiate into different tissues
1. _______derm (outer layer) eventually becomes:
a.
b.
2.
__________________ of the skin and its derivatives
____________ tissue - brain, spinal cord, sense organs, pituitary gland, & adrenal
medulla
________derm (middle layer) differentiates to form:
a.
b.
c.
d.
e.
f.
________________ - smooth, cardiac, & skeletal
a.
Epithelial lining (____________ membranes) of digestive sys., respiratory sys.,
urinary bladder & urethra, and vagina
b.
___________ & pancreas
________________ tissue - cartilage, bone, ligaments, & blood
_____________ of the skin
__________ lining of blood vessels, body cavities, joint cavities
________________, which becomes the intervertebral nucleus pulposus
______________, kidneys, ureters, and adrenal cortex
3. ________derm (inner layer) eventually forms:
C. Extraembryonic _________________ include the amnion, yolk sac, allantois, and
chorion
1.
__________________ - thin membrane derived from ectoderm and mesoderm, it
surrounds the embryo, forming an amniotic sac filled with amniotic fluid.
a.
Functions include:
1) Ensures ___________________ growth & development
3
2) __________________ & protects the embryo/fetus
3) Helps maintain a constant pressure & _______________
4) Permits freedom of fetal _________________
2.
3.
b.
Amniotic fluid is composed of fluids from maternal blood, fetal ___________,
and cells sloughed off by the fetus
c.
In _______________________, amniotic fluid is withdrawn by syringe (at 14-15
wks), then the cells are tested for genetic abnormalities
_________ sac - established from cells on the underside of the embryonic disc during
the end of the 2nd week
a.
b.
c.
Does ____ contain nutritive yolk
d.
Folds with the embryonic disc to become the primitive _____ and part of the
umbilical cord
Primordial ________ cells form from the yolk sac wall, then migrate to the
gonads to form spermatogonia or oogonia
__________________ - forms during the 3rd week as a small outpocketing near the
base of the yolk sac
a.
b.
c.
4.
Produces _________ cells until the liver forms the 6th week
It is involved in __________ cell formation
Gives rise to the fetal arteries and vein in the _____________
Contributes to urinary _______________ development
_________________ - outermost extraembryonic membrane
a.
Becomes the fetal half of the _______________ as fingerlike villi extend into the
endometrium
b.
The villous chorion forms embryonic __________________; as the embryonic
heart forms, the blood is circulated close to the uterine wall
c.
In chorionic villus sampling, a sample of chorionic _______ is obtained (at 1012 wks), then is tested for genetic abnormalities
D. _______________ - vascular structure formed from both maternal & embryonic tissues
that attach the fetus to the mother’s uterus
1.
Blood does ____ flow directly between mother & fetus, rather substances diffuse
across the shared placental membrane
a.
____________ and nutrients diffuse across the placenta from mother to fetus via
blood in the umbilical vein
b.
_________________ and wastes diffuse from fetus to mother via blood carried by
the umbilical arteries
c.
The placenta’s ____________________ prevents some large pathogens from
diffusing but allows smaller pathogens, such as drugs, viruses, some bacteria, and
maternal antibodies
2. The placenta also functions as an __________________ gland, secreting both
glycoprotein and steroid hormones to maintain the endometrium.
E. _________________ cord - connects the fetus to the placenta and contains 2 umbilical
arteries & 1 umbilical vein
4
F. Major structural changes in the embryo by week
1. Third week – _______________ & neurulation occur
a. A linear band called the primitive __________ occurs along the dorsal midline of
the embryonic disk and cells invaginate
2.
3.
b.
This gives rise to the primitive _________ at the cranial end, which gives rise to
the mesoderm of the head and notochord
c.
The _____________ and somites form along the midline axis to begin formation
of the embryonic skeleton and muscles
d.
Along the dorsal midline ectoderm above the notochord a neural plate forms,
which folds into a neural groove, then a ____________, from which the brain
and spinal cord develop
Fourth week – embryo folds into a tadpole shape, germ layers __________________
into specialized tissues
a.
A connecting stalk that will become the _______________ cord forms from the
embryo to the placenta
b.
c.
d.
e.
The _________ begins pumping
Superior & inferior ___________ are seen as small swellings
_________________ form from the limb buds, with paddle shaped- hand & foot
plates
Sixth week
a. The ________ is larger than the trunk
b.
c.
5.
Primordial ______, brain, spinal cord, lungs, & digestive organs develop
Fifth week
a. The head enlarges and the developing eyes, ears, and ______ _______ become
obvious
b.
4.
_________ & jaws become apparent
The _________ is undergoing extensive differentiation
Limbs lengthen and are flexed, with ___________ appearing between the digital
rays in the hand & foot plates
Seventh & eighth weeks
a. Body __________ are formed
b.
c.
d.
e.
f.
g.
The _________ system is starting to coordinate body activity
h.
From this time on, the embryo is called a __________
_______ is apparent
______ are well developed, but lids are stuck together
_________ are developed but plugged with mucus
External ____________ are formed, but still undifferentiated
All body systems are ________________ (but still immature) by the end of the 8th
week
5
G. The developing embryo/fetus is particularly susceptible to __________________ (birth
defect causing substances) during the first ________________ (first 3 months of
development.