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Fertilization results in a ______________.
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?
The plasma membrane of the egg is surrounded by an extracellular matrix called the _________________.
Zona of pellucida is surrounded by a few layers of follicle cells collectively called the _____________.
*these cells nourish the egg when it was in the follicle of the ovary
The first barrier the sperm must penetrate is the ______________.
*Enzymes secreted by the sperm aid in penetration of the corona radiata
The _____________ is responsible for penetrating the zona pellucida.
*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 ________________.
*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.
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 ______________.
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.
*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 ______________.
Early embryonic development is characterized by a series of rapid mitotic divisons known as ______________.
- 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.
A ________________ results in cells whose future differentiation pathways are determined at an early development stage.
*differentiation is the specialization of cells that occurs during development.
The first complete cleavage of the zygote occurs approximately ______________ after fertilization.
- 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 ____________.
zygote --- morula --- blastula
____________ begins when the morula develops a fluid filled cavity called the blastocoel.
The mammalian blastula is called a ______________.
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 ______________.
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.
*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 ______________.
*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 later develops into the _______________.
The opening of the archenteron is called the _______________.
In organisms classified as deuterostomes (such as humans), the blastophore is the future site of the ___________.
In organisms classified as protostomes, the blastophore is the site of the future ____________.
- Integument (includes epidermis, hair, nails, and epithelium of the nose, mouth, and anal canal)
- lens of the eye
- nervous system
- Epithelial linings of the digestive respiratory tracts (including lungs)
- parts of the liver, pancreas, thyroid, and bladder
- musculoskeletal system
- circulatory system
- excretory system
- 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.
A rod of mesodermal cells, called the_______________, develops along the longitudinal axis just under the dorsal layer of ectoderm.
- *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 ________________.
- Peripheral nervous system
- *sensory ganglia, autonomic ganglia, adrenal medulla, schwann cells
The embryo is referred to as a fetus after 8 weeks of gestation.
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. placenta
- 2. umbilical cord
The placenta and umbilical cord are outgrowths of the four extra embryonic membranes formed during development:
- 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
During fetal development, the ___________ lies next to the shell and carries out gas exchange.
Durin fetal development, the _______________ collects nitrogenous wastes.
During fetal development, the _______________ provides nourishment to the fetus.
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.
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.
___________________ are able to diffuse across maternal capillaries into fetal blood.
C. Amino Acids
E. Inorganic salts
F. all the above
all the above
Fetal hemoglobin (Hb-F) has __________ affinity for oxygen than does adult hemoglobin (Hb-A).
_________________________ 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.
- *Maternal blood and fetal blood do not mix!
Material between maternal and fetal blood vessels occurs in the placenta via ______________.
In addition to nutritive and respiratory functions, the placenta offers the fetus some immunological protection by preventing the diffusion of foreign material/bacteria.
Placenta is permeable to _____________.
C. alcohol, drugs
d. both B and C.
Both B and C
The placenta also functions as an _______________, by producing hormones.
The placenta produces hormones such as
- 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.
- *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. ductus venosus
- 2. foramen ovale
- 3. ductus arteriosus
The ______________ carries oygenated blood from the placenta to the fetus.
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.
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.
Deoxygenated blood is returned to the placenta via _________________.
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: 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.
- infant begins to produce adult hemoglobin