A sperm has 3 distinct parts: _____________, _____________, _____________.
Head, middle piece, and a tail
What does the head of the sperm contain?
contains nucleus and is capped by a membrane bounded acrosome
What does the middle piece of the sperm contain?
energy producing mitochondria
What does the tail of the sperm contain?
Flagellum
The plasma membrane of the egg is surrounded by an extracellular matrix called the _________________.
zona pellucida
Zona of pellucida is surrounded by a few layers of follicle cells collectively called the _____________.
Corona radiata
*these cells nourish the egg when it was in the follicle of the ovary
The first barrier the sperm must penetrate is the ______________.
Corona radiata
*Enzymes secreted by the sperm aid in penetration of the corona radiata
The _____________ is responsible for penetrating the zona pellucida.
acrosome
*acrosome releases enzymes that digest the zona pellucida, allowing the sperm to come into direct contact with the ovum cell membrane
During fertilization, once the sperm is in contact with ovum's cell membrane, the sperm forms a tube-like structure called ________________.
Acrosomal Process
*extends to the cell membrane and penetrates it, fusing the sperm cell membrane with that of the ovum.
One the sperm nucleus enters the ovum's cytoplasm, at which stage of meiosis does this occur?
Meiosis II is complete
The acrosomal reaction triggers a ______________ in the ovum.
cortical reaction
What does the cortical reaction cause?
Causes calcium ions to be released into the cytoplasm
The release of the calcium ions into the cytoplasm during the cortical reaction initiates the formation of the ______________.
Fertilization membrane
cortical reaction ---- calcium released -- formation of fertilization membrane
What is the fertilization membrane?
Fertilization membrane ia hard layer that surrounds the ovum cell membrane and prevents multiple fertilizations.
The release of the calcium ions during the cortical reaction also stimulates metabolic changes within the ovum, greatly increasing its metabolic rate.
A. True
B. False
True
*This is followed by the fusion of the sperm nucleus with the ovum nucleus to form a diploid zygote
The fusion of the sperm nucleus and ovum's nucleus results to a ______________.
Diploid zygote
Early embryonic development is characterized by a series of rapid mitotic divisons known as ______________.
Cleavages.
lead to an increase in cell number without a corresponding growth in cytoplasm
*total volume of cytoplasm remains constant
*Thus, cleavage results in progessively smaller cells with an increasing ratioi of nuclear-to-cytolasmic material.
*also increases the surface-to-volime ratio of each cell ----thus, improving gas&nutrient exchange
An _________________ is one that results in cells that maintain the ability to develop into a complete organism.
Indeterminate cleavage
A ________________ results in cells whose future differentiation pathways are determined at an early development stage.
Determinate cleavage
*differentiation is the specialization of cells that occurs during development.
The first complete cleavage of the zygote occurs approximately ______________ after fertilization.
32 hrs
2nd cleavage - 60 hrs
third cleavage - 72 hrs ---- at which, the 8-cell embryo reaches the uterus.
As cell division continues, zygote turns into a ____________.
Morula
zygote --- morula --- blastula
____________ begins when the morula develops a fluid filled cavity called the blastocoel.
Blastulation
The mammalian blastula is called a ______________.
Blastocyst
The blastocyst consists of 2 cell groups: _______________,_______________.
Inner cell mass -protrudes into the blastocoel
trophoblast-surrounds the blastocoel and later gives rise to the chorion
The trophoblast later gives rise to the ______________.
Chorion
The embryo implants in the _____________ during blastulation.
uterine wall, approximately 5-8 weeks after fertilization
The uterus is prepared for implantation by the hormone, ________________.
Progesterone - causes glandular proliferation in the endometrium.
What is the endometrium?
Mucosal lining of the uterus.
Embryonic cells secrete ________________ that enable the embryo to digest tissue and implant itself in the endometrium.
Proteolytic Enzymes
*Eventually, maternal and fetal blood exchange materials at this site, later to be the location of the placenta.
Once implanted, cell migrations transform the single cell layer of the blastula into a 3 layered structure called a ______________.
Gastrula.
*Any in pocketing forms as cells continue to move toward the invagination, eventually eliminating the blastocoel. The result is a two layered cup.
The newly formed cavity of the two-layered gastrula is called the ________________.
Archenteron
Archenteron later develops into the _______________.
Gut.
The opening of the archenteron is called the _______________.
Blastophore
In organisms classified as deuterostomes (such as humans), the blastophore is the future site of the ___________.
Anus.
In organisms classified as protostomes, the blastophore is the site of the future ____________.
Mouth
Ectoderm
Integument (includes epidermis, hair, nails, and epithelium of the nose, mouth, and anal canal)
lens of the eye
nervous system
Endoderm
Epithelial linings of the digestive respiratory tracts (including lungs)
parts of the liver, pancreas, thyroid, and bladder
Mesoderm
musculoskeletal system
circulatory system
excretory system
gonads,
Connective tissue throughout the body
portions of the digestive and respiratory organs
By the end of gastrulation, regions of the germ layers begin to develop into a _______________, this process is known as neurulation.
Nervous system
A rod of mesodermal cells, called the_______________, develops along the longitudinal axis just under the dorsal layer of ectoderm.
Notochord
*notochord has an inductive effect on the overlying ectoderm, causing it to bend inward and form a groove along the dorsal surface of the embryo.
*The dorsal ectoderm folds on either side of the groove; these neural folds grow upward and finally fuse, forming a closed tube.
*This closed tube is the neural tube - gives rise to the brain and spinal cord (Central nervous system)
Neural tube gives rise to the __________ and ____________.
Brain and Spinal Cord
*Central Nervous System
During neurulation, the cells at the tip of each neural fold are called the ______________ cells.
Neural crest cells.
*These cells migrate and give rise to the peripheral nervous system, including sensory ganglia, autonomic ganglia, adrenal medulla, and Schwann cells.
The neural crest cells give rise to the ________________.
The embryo is referred to as a fetus after 8 weeks of gestation.
A. True
B. False
True
The growing fetus' specialized circulatory system does:
a. receives oxygen directly from its mother
b. supplies nutrients to the fetus
c. removes carbon dioxide and metabolic wastes
d. all the above.
All the above!
The two components of the fetus' specialized circulatory system :
1. _________________
2. _________________
1. placenta
2. umbilical cord
The placenta and umbilical cord are outgrowths of the four extra embryonic membranes formed during development:
1. ____________
2. ____________
3. ____________
4. ____________
1. amnion.
2. allantois
3. chorion
4. yolk sac
__________ acts as a shock absorber of external and localized pressure from the uterine contractions during labor
amniotic fluid
During fetal development, the ___________ lies next to the shell and carries out gas exchange.
Chorion
Durin fetal development, the _______________ collects nitrogenous wastes.
allantois
During fetal development, the _______________ provides nourishment to the fetus.
yolk sac
The chorion, amnion, allantois, and yolk sac are also known as _________________.
Extra-embryonic membranes - develop from extensions of the germ layers.
Found in humans and chicks.
During fetal development, the ________________ become closely associated with endometrial cells, developing into the spongy tissue of the placenta.
Chorionic villi
The blood vessels of the allantoic wall enlarge and become the _________________.
Umbilical vessels : connect the fetus to the developing placenta.
At some point during fetal development, the ___________ and the ____________ are enveloped by the amnion, forming the primitive umbilical cord.
Allantois and yolk sac
The _______________ is the site of nutrition, respiration, and waste disposal for the fetus.
Placenta
___________________ are able to diffuse across maternal capillaries into fetal blood.
A. water
B. Glucose
C. Amino Acids
D. Vitamins
E. Inorganic salts
F. all the above
all the above
Fetal hemoglobin (Hb-F) has __________ affinity for oxygen than does adult hemoglobin (Hb-A).
A. Lesser
B. Greater
greater
_________________________ diffuse in the opposite direction --- from fetal blood into maternal blood.
Metabolic wastes and carbon dioxide
Circulatory system of mother and fetus are not directly connected.
A. True
B. False
True!
*Maternal blood and fetal blood do not mix!
Material between maternal and fetal blood vessels occurs in the placenta via ______________.
Diffusion
In addition to nutritive and respiratory functions, the placenta offers the fetus some immunological protection by preventing the diffusion of foreign material/bacteria.
A. True
B. False
True.
Placenta is permeable to _____________.
A. Bacteria
B. viruses.
C. alcohol, drugs
d. both B and C.
Both B and C
The placenta also functions as an _______________, by producing hormones.
Edocrine gland
The placenta produces hormones such as
1. ________________
2. ________________
3.________________
1. progesterone
2. estrogen
3. human chorionic gonadotropin (HCG)
The presence of ___________________ in urine is the simplest test for pregnancy.
HCG - human chorionic gonadtropin
The major difference in fetal circulation is that, blood is oxygenated in the ____________, while in adults the blood is oxygenated in the lungs.
Placenta.
*This is because fetal lungs do not become functional until after birth.
The fetal circulatory route contains 3 shunts that divert blood flow away from the developing fetal liver and lungs.
1. _______________
2. _______________
3. _______________
1. ductus venosus
2. foramen ovale
3. ductus arteriosus
The ______________ carries oygenated blood from the placenta to the fetus.
umbilical vein
In fetal circulation, the blood bypasses the fetal liver by way of a shunt called the __________________, before converging with the inferior vena cava
ductus venosus
*Since the oxygenated blood from the umbilical vein mixes with the deoxygenated blood of the venae cavae, the blood entering the right atrium is only partially oxygenated.
In fetal circulation, blood bypasses the pulmonary circulation and enters the left atrium directly from the right atrium by way of the ___________________, a shunt that diverts blood away from the pulmonary arteries.
Foramen Ovale
In fetal circulation, the remaining blood in the right atrium empties into the right ventricle and is pumped into the pulmonary artery. Most of this blood is shunted directly from the pulmonary artery to the aorta via the ____________________.
Ductus Arteriosus- monary arteries carry
In the fetus, the pulmonary arteries are partially oxygenated to the lungs.
A. True
B. False
True
Deoxygenated blood is returned to the placenta via _________________.
Umbilical arteries
Which arteries are the only arteries that carry deoxygenated blood?
Fetal umbilical artery and adult pulmonary arteries.
Which veins are the only veins that transport oxygenated blood?
Fetal umbilical vein
Adult pulmonary vein
Human pregnancy, or _______________, is approximately 9 months.
Gestation.
Gestation: First Trimester: 8 weeks
major organs begin to develop:
eyes, gonads, limb, and liver start to form
still an embryo in the beginning of the trimester
cartilaginous skeleton begins to turn into bone by the 7th week
by the 8th week, most organs have formed
brain is fairly developed
embryo is referred to as a fetus
Gestation: Second Trimester
fetus does a tremendous amount of growing
moves around amniotic fluid
face appears human
toes and fingers elongate
Gestation: Third Trimester
continued rapid growth and further brain development
*antibodies are transported by highly selective transport from the mother to fetus
growth rate slows as the fetus becomes less active, as it has less room to move about
After birth, a number of changes occur in the circulatory system of the fetus:
lungs expand with air and rhythmic breathing begins
resistance in the pulmonary blood vessels decreases- causes an increase in blood flow through the lungs
umbilical blood flow stops
blood pressure in the inferior vena cava decreases - causing a decrease in pressure in the right atrium
left atrial pressure increases due to the increased blood flow from the lungs
increased left atrial pressure coupled with decreased right atrial pressure causes the foramen ovale to close
ductus arteriosus constricts and later closes permanently.
ductus venosus - degenerates over time, completely closing in most infants 3 months after birth.
