Biology Ch. 3 Flashcards
Fertilization occurs in the ____
Ampulla of the fallopian tube
The tubular acrosomal apparatus is formed when the ____ and does ____
first sperm contacts the secondary oocyte’s cell membrane; it extends into the cell membrane so that the pronucleus can enter the oocyte
What occurs after the penetration of the tubular acrosomal apparatus?
A cortical reaction releases calcium ions to depolarize the ovum’s membrane
Why does the ovum’s membrane depolarize after contact with sperm?
to prevent further fertilization and increase the metabolic rate of the diploid zygote
Dizygotic/fraternal twins form from ____
the fertilization of 2 different eggs released during one ovulatory cycle by 2 different sperm
Monozygotic/identical twins form from _____
Indeterminate cleavage: a single zygote splitting into two
If a zygote incompletely divides, this forms ____
Conjoined twins
Define monochorionic/monoamniotic twins
Identical twins that share the same amnion and chorion
Define monochorionic/diamniotic twins
Identical twins that share same the chorion but different amnion
Define dichorionic/diamniotic twins
Identical twins that have separate amnions and chorions
The ____ of a zygote forms an embryo
First cleavage
List the two types of zygotic cleavage
1) Indeterminate
2) Determinate
Define indeterminate cleavage
results in cells that can develop into complete organisms
Define determinate cleavage
results in cells with predetermined fates- will differentiate into a specific cell type
A blastula forms from ___
Basculation of the morula
Define morula
A solid ball of cells resulting from division of a fertilized ovum, and from which a blastula is formed.
A blastula is compose of ____
Blastocoel (fluid-filled cavity)
Define blastocyst
Human blastula
Blastulas are composed of ____
Blastocoel, inner cell mass, trophoblast
The trophoblast cells will form ____
Chorion, then placenta
The inner cell mass will form ____
the organism
Chorionic villi form from ____
The chorion
Describe the function of chorionic villi
Support maternal-fetal gas exchange
Describe the structures and mechanisms involved in fetal-maternal gas exchange
The veins of the umbilical cord carry oxygenated blood from the placenta to the embryo
The arteries of the umbilical cord carry deoxygenated blood and water from the embryo to the placenta
Early blood cell development occurs in the ____
yolk sac
Describe the function of the yolk sac
Supports the embryo until the placenta is functional, is the site of early blood cell development
Define allantois
The extraembryonic membrane that is involved in early fluid exchange between the embryo and yolk sac
The umbilical cord is formed from ___
The yolk sac and allantois
Define amnion and it’s function
It’s a fluid-filled extraembryonic membrane that acts as a shock absorber
Define gastrulation
The generation of 3 distinct cell layers
Describe the steps of gastrulation
The invagination in the blastula causes __ to merge and forms ___
Archenteron membranes merge to form gastrula
The archenteron membranes develop into the ____
Gut
The opening of the archenteron is ___
the blastopore
In deuterostomes, the blastopore develops into ___
the anus
In protostomes, the blastopore develops into ___
the mouth
Define primary germ layers
3 layers of cells that have migrated into the blastocoel (ectoderm, mesoderm, endoderm)
Define ectoderm
The outermost layer that forms integument (i.e. epidermis, hair, nails) epithelia of nose, mouth, and lower anal canal, lens of the eye, nervous system (adrenal medulla) and inner ear
Define mesoderm
The middle layer that develops into different systems, including musculoskeletal, circulatory, and excretory systems, in addition to gonads, muscular and connective tissue layers of the digestive and respiratory systems, and adrenal cortex
Define endoderm
The innermost layer that forms epithelial linings of digestive and respiratory tracts (i.e. lungs), pancreas, thyroid, bladder, distal urinary tracts, and parts of liver
Define spina bifida
some or all of spinal cord is open
Define anencephaly
skull is left open and brain doesn’t develop
What causes spina bifida and anencephaly
The neural tube doesn’t close
Define teratogens
substances the interfere with development of the embryo, i.e. alcohol, drugs, viruses, environmental chemicals
Overexposure to sugar in utero can cause ____
a fetus that is too large to be delivered and suffers form hypoglycemia (due to high levels of insulin synthesized to compensate)
What can prevent the complete closure of the neural tube?
Maternal folic acid deficiency
Define specificiation
The initial stage of cell specialization, in which cell is reversibly designated as a specific cell type
Define determination
The irrevocable commitment of cell to a particular future function and lineage
Which is first: specificiation or determination?
Specificiation
Define morphogens
molecules that cause determination to occur
Define differentiation
The changing of cells structure, function, and biochemistry to match the cell type established during determination
Tissues that a stem cell can differentiate into is determined by ____
Potency
As cells become more differentiated, potency (decreases/increases)
Decreases
Define totipotent
Cells with the greatest potency (i.e. embryonic stem cells)
Embryonic stem cells are derived from ___
The inner cell mass of a blastocyst
Define pluripotent
Cells that can differentiate into any cell type except for those found in placental structures
Pluripotent stems are only formed after ____
totipotent cells differentiate into germ cell layers
Define multipotent
cells that can differentiate into multiple types of cells within a particular group
Hematopoietic cells are cells that can differentiate into any blood cells, but not any other cell type. A hematopoietic cell is an example of what type of cell?
Multipotent
Define induction
The ability of 1 group of cells to influence the fate of nearby cells
Induction is mediated by __
Inducers
Define growth factors
peptides that promote differentiation and mitosis in certain tissues
Inducers are usually ___
Growth factors
Define reciprocal development
During induction, when cells mutually induce differentiation of one another
What ensures that different cell types that work together will remain in proximity to one another
Inducers
The cell that is induced is called a ___
Responder
A responder must be ___ to be induced
Competent (able to respond to an inducing signal)
Define autocrine signal
acts on the same cell that secreted first signal
Define paracrine signals
act on cells in local area
Define juxtacrine signals
involve a cell directly stimulating receptors of an adjacent cell
Define endocrine signals
involve secreted hormones that travel through bloodstream to distant target tissue
Define apoptotic blebs
Self-contained protrusions on a cell about to undergo apoptosis
Apoptotic blebs are broken into ___
apoptotic bodies
Define complete regeneration
lost or damaged tissues completely replaced
Define incomplete regeneration
newly formed tissue is not identical to lost tissue
Define senescence
biological aging that can occur at cellular and organismal level
Define telomerase? What cells is it found on?
a reverse transcriptase enzyme that is able to synthesize the ends of chromosomes and prevent senescence; germ, fetal, and tumor cells
(Higher/Lower) partial pressure of oxygen in maternal blood than fetal blood allows diffusion of oxygen across placental barrier
Higher
Define fetal hemoglobin (HbF) and it’s function
Fetal blood cells; its greater affinity for O2 assists in the transfer and retention of oxygen in the fetal circulatory system
Fetal hemoglobin has a (greater/lesser) affinity for O2
Greater
The placenta is a __ organ
Endocrine
List the hormones produced by the placenta
Estrogen, progesterone, and hCG
Describe the process of fetal detoxification and metabolism
Detoxification and metabolism are controlled by the maternal liver, nutrient and waste exchange occurs at placenta
The fetal lungs and liver are sensitive to high blood pressures in postnatal life. How does the body respond to thisl?
The formation of 3 shunts to direct blood away from the lungs and liver
List the 3 fetal shunts
1) foramen ovale
2) ductus arteriosus
3) ductus venosus
Describe the structure and function of the foramen ovale
It’s a one way valve that connects the left and right atria; Allows blood entering right atrium from inferior vena cava to flow into the left atrium instead of right ventricle and therefore directly into the aorta and systemic circulation. It shuts at birth to reverse the pressure differential
The ___ side of the heart is at higher pressure in a fetus
Right
At birth, the ___ is shut to reverse the pressure differential of the fetal hear
Foramen ovale
Describe the function of the ductus arteriosus
shunts leftover blood from pulmonary artery to aorta
Describe the function of the ductus venosus
shunts blood returning from placenta directly into the inferior vena cava, bypassing the liver
How does the liver receive blood?
from small hepatic arteries
Describe the events of the first trimester
Major organs develop, heart beats partway through, eyes, gonads, limbs, and liver form
Cartilaginous skeleton hardens into bone (by 7th week)
Most of organs and much of brain is developed by 8 weeks
Describe the major events of the second trimester
Movement in amniotic fluid, face takes on appearance, toes and fingers elongate
How large is the fetus during the first trimester
9cm
How large is the fetus during the second trimester
30-36 cm
Describe the events of the third trimester
Rapid growth and brain development initially, followed by slowed growth rate toward end of trimester
Antibodies transported from mother to fetus at highest
Fetus becomes less active
Contractions are stimulated by ___
prostaglandins and oxytocin
Oxytocin is an example of a ____ hormone
Peptide
Describe the 3 events of parturition
1) Cervix thins and amniotic sac ruptures
2) Contractions expel fetus
3) Placental and umbilical are expelled (afterbirth)
