Embryology and Fetal Development Flashcards
(50 cards)
What happens in the embryonic period of development?
First 8 weeks- cells divide, tissues and organs form, structures the support and nourish the developing embryo form
What happens in the fetal period of development?
8 weeks to birth- body grows rapidly and organ begin to function and coordinate to form organ systems
How many chromosomes are in a human zygote? Where do they originate from?
A human zygote has 46 chromosomes. 23 from the sperm and 23 form the egg. They pair up at fertilization (23 pairs=46) *Male determines sex of zygote
Why does an egg have to be fertilized within 12-24 hours?
The egg loses its capacity to develop further after 24 hours. It starts to degenerate after 24 hours.
Why do only a few sperm arrive in the oviduct where the egg is?
The vagina is acidic (where many sperm are killed, only one oviduct has the egg (only one ovary releases an egg each month) and many sperm travel up the wrong oviduct.
What is the chromosome layout for boys and girls?
44 + XX=girl, 44+XY= boy
Why doesn’t the first sperm that reaches the egg enter and join with it?
It takes the action of many sperm and the enzyme in their acrosomes to break through the jelly coat of an egg. The first sperm that arrives needs the help of many other to get through this barrier, and a sperm arriving later will get in first
Define fertilization?
When the sperm and egg nucleus fuse
Define cleavage, where does it occur?
Cell division without enlargement of the cell. It occurs in the Fallopian Tubes (oviduct)
Flow chart from zygote to blastocyst
Zygote-> 2 cells-> 4 cells-> 8 cells-> 16 cells (morula)-> blastocyst (fluid filled space)
Name and describe the layers of a blastocyst
Out Cell Mass: trophoblast (becomes chorion, secretes hCG-> maintains Corpus Luteum)
Inner Cell Mass: fluid filled space turns into embryo
Flow Chart from ovulation to implantation.
Ovulation-> fertilization-> cleavage-> morula-> early blastocyst-> implantation
Flow Chart about an egg from ovary to outer cell mass of a zygote
Ovary-> fimbriae-> ovum-> fertilization with sperm-> zygote-> 2 cell stage-> 4 cell stage-> 8 cell stage-> 16 cell stage (morula)-> inner cell mass-> outer cell mass.
What is the process of cleavage?
Cell division (mitosis) that increases the number of cells in the embryo but doesn’t increase the size of the embryo
What group of cells does the embryo develop from?
Inner cell mass (embryoblast)
What is implantation?
When the blastocyst buries itself into the endometrium. The trophoblasts (outer cell mass) secretes enzymes to digest parts of the endometrium and the blastocyst sinks into the lining of the uterus. The endometrium now supplies the embryo w/ enough nutrients.
What is hCG and how long is it secreted for?
It is a hormone by the trophoblasts for the first trimester of pregnancy. It has the same action of LH- it maintains the CL thus the Cl will not degenerate but will continue to produce progesterone and estrogen to maintain the endometrium lining.
What is the amniotic cavity?
When a space begins to form between the inner cell mass and the trophoblast
What happens as the amniotic cavity forms?
The inner cell mass flattens into a disk shape. The disk consists of 2 layers then develops a 3rd.The outer ectoderm, inner endoderm, and the the mesoderm in between the two. This forms the body of the embryo
What is the process called forming the three layers? What is the names of these three layers? Identify the name if the developing embryo at this time?
Gastrulation. Primary Germ Layer. Gastrula
Define morphogenesis
The series of events that form distinct structures of a developing organism, gastrulation marks the beginning of this process and how the human body takes shape
Define differentiation (specialization)
Cellular process that enables a cell to develop a particular shape and to preform specific functions. Once you are a blastocyst, cells begin to take their set functions and are called “specialized cells”
How are the development of primary germ layers related to differentiation?
The development of the three germ layers (gastrulation) is the START of differentiation. All body cells originate from three layers.
Identify 3 structures that form the: Ectoderm
Skin, hair, nails, brain, NS, eyes, pituitary gland, adrenal medulla (Outer Layer)
