Biology Chapter 3: Embryogenesis and Development Flashcards
What is fertilization?
The joining of a sperm and an ovum
Where does fertilization occur?
ampulla of the fallopian tube
What does sperm use to penetrate the corona radiata and zona pellucida?
Uses acrosomal enzymes
What happens when the sperm contacts the oocytes plasma membrane?
Establishes the acrosomal apparatus and injects its nucleus
What is the cortical reaction?
A sperm penetrates, causing a release of calcium ions, preventing additional sperm from fertilizing the egg and increases the metabolic rate of the resulting diploid zygote.
How do fraternal twins result?
Fertilization of two eggs by two different sperm
How do identical twins result?
Splitting of a zygote in two
What is cleavage?
Early divisions of cells in the embryo - result in a larger number of smaller cells, as the overall volume does not change.
When does the zygote turn into an embryo?
After 1 division
What is indeterminate cleavage?
results in cells that are capable of becoming any cell in the organism.
What is determinate cleavage?
results in cells that are committed to differentiating into a specific cell type
What is a morula?
solid mass of cells seen in early development
What is the blastula?
has a fluid-filled center called a blastocoel and two different cell types, including trophoblasts and inner cell mass
Where does the blastula implant?
in the endometrial lining and forms the placenta
What is the chorion?
contains the chorionic villi, which penetrates the endometrium and create the interface between maternal and fetal blood.
What supports the embryo?
It is supported by the yolk sac.
What is the allantois?
It is involved in early fluid exchange between the embryo and the yolk sac
What is the amnion?
Lies just inside the chorion and produces amniotic fluid
How is the organism connected to the placenta?
The umbilical cord
What happens during gastrulation?
The archenteron is formed with a blastopore at the end. As it grows through the blastocoel, it contacts the opposite side, establishing the three primary germ layers.
What does the ectoderm become?
The epidermis, hair, nails, epithelia of the nose, mouth and anal canal, nervous system and lens of the eye
What does the mesoderm become?
Much of the musculoskeletal, circulatory and excretory systems, gonads, connective tissue layers of the digestive and respiratory systems, adrenal cortex
What does the endoderm become?
Becomes much of the epithelial lining of the respiratory and digestive tract, parts of the pancreas, thyroid, bladder and distal urinary tracts.
What is neurulation?
development of the nervous system and begins after the formation of the three germ layers.
What are the steps to neurulation?
- Notochord induces a group of ectodermal cells to form new folds
- The neural folds fuse to form the neural tube, which becomes the central nervous system
- The tip of each fold becomes the peripheral nervous system.
What are teratogens?
substances that interfere with development, causing defects or even death of the developing embryo
What is determination?
commitment to a specific cell lineage, which may be accomplished by uneven segregation of cellular material during mitosis or morphogens.
What is differentiation?
Refers to the changes a cell undergoes due to selective transcription to take on characteristics appropriate to its cell line.
What are stem cells?
Cells that are capable of developing into various cell types. They can be classified by potency.
Totipotent cells
able to differentiate into all cell types including the three germ layers and placental structures.
Pluripotent cells
Able to differentiate into all three of the germ layers and their derivatives.
Multipotent cells
Able to differentiate only into a specific subset of cell types
Autocrine signals
act on the same cell that released the signal
Paracrine signals
act on cells in the local area
Juxtacrine signals
act through direct stimulation of the adjacent cell
Endocrine signals
act on distant tissues after traveling through the blood stream.
Growth factors
peptides that promote differentiation and mitosis in certain tissues
Reciprocal induction
When two tissues induce further differentiation in each other
Apoptosis
programmed cell death via the formation of apoptotic blebs that can be absorbed and digested by other cells
What are uses of apoptosis?
To form certain anatomical structures or removing damaged cells
What is regenerative capacity?
The ability of an organism to regrow certain parts of the body. The liver has high regenerative capacity, while the heart has low regenerative capacity.
What is senescence?
The result of multiple molecular and metabolic processes, e.g. the shortening of telomeres during cell division.
What is exchanged at the placenta?
Nutrients, gas and waste
What is the difference in the fetal hemoglobin?
It has higher affinity for oxygen, which assists in the transfer and retention
What does the placenta secrete?
estrogen, progesterone, and hCG
What are the three shunts of the fetal circulatory system?
- Foramen ovale - r.a. to the left. atrium, bypassing the lungs
- Ductus arteriosus - connects the pulmonary artery to the aorta, bypassing the lungs
- Ductus venosus - connects the umbilical vein to the inferior vena cava, bypassing the liver
What happens in the first trimester?
organogenesis occurs (development of heart, eyes, gonads, limbs, liver, brain)
What happens in the second trimester?
tremendous growth, movement begins and it becomes distinctly human, digets elongate
What happens in the third trimester?
Rapid growth and brain development continue and antibodies are transferred to the fetus
What are contractions coordinated by?
prostaglandins and oxytocin
