Embryology McKinley and O’Laughlin Chapter 3
May 08, 2015
Embryology
McKinley and O’Laughlin
Chapter 3
Introduction
All of the bodies cells arise from the zygote (fertilized egg).
We get our ~100 trillion cells from Mitosis, the production of 2 genetically identical daughter cells from 1 parental cell.
Introduction
What is the process which results in these cells specializing? Differentiation
Introduction
What is the 38-week period of development in the female reproductive system? Prenatal period
A 40 week gestation period is measured from the woman's last period, not ovulation.
Introduction
What is the study of development during this period (prenatal development)? Embryology
Introduction
What is the biological specialty that studies anatomical and physiological changes from the conception of a new individual to that individuals death? Developmental Biology
Introduction
What are the 3 periods of development from the moment of conception to birth? Pre-embryonic period Embryonic period Fetal period
Gametogenesis
What are haploid cells which are capable of producing a new diploid individual? Gametes
Gametogenesis
What are diploid cells which are distinguished from the gametes? Somatic cells
Gametogenesis
What is the distinguishing characteristic of human diploid cells? Carry 23 pairs of chromosomes
We aren’t the only species with 23 pairs, but our closest relatives have 24 pairs.
Gametogenesis
What is the distinguishing characteristic of human haploid cells? Carry 23 chromosomes
1 member of each pair Crossing over makes each chromosome different
than those receive from parents
Gametogenesis
What type of cell division produces haploid cells? Meiosis
Gametogenesis
Mitosis 2, diploid daughter
cells
Meiosis 4, haploid daughter
cells Crossing over:
Exchange of DNA between homologues
How do these 2 types of cell division (Mitosis and Meiosis) differ?
Meiosis I
Gametogenesis
Where in the body does reduction division occur? Gonads
Gametogenesis
Why is reduction division so important?
Pre-embryonic Period
What is the fertilized egg? Zygote
Pre-embryonic Period
What period of development ranges from the moment of conception until the completion of implantation into the uterine wall? Pre-embryonic
Pre-embryonic Period
What process restores the diploid number of chromosomes, determines the sex of an individual, and initiates cleavage? Fertilization
Pre-embryonic Period
Where does this process usually take place? Uterine tube (Ampulla)
Pre-embryonic Period
What series of synchronized mitotic divisions results in an increase in the number of cells? Cleavage
Pre-embryonic Period
What is the compacted 16-cell stage of development? Morula
Pre-embryonic Period
In what stage do the products of conception enter the uterus? Morula
Pre-embryonic Period
What stage of development occurs as fluids enter the products of conception (Morula at this point)? Blastocyst
Pre-embryonic Period
What are the two distinct components of this fluid-filled sphere? Which becomes the embryo? Trophoblast: becomes the chorion Embryoblast: becomes the embryo
Pre-embryonic Period
What is the process by which this sphere burrows into and embeds within the endometrium? Implantation
Pre-embryonic Period
When does the process (Implantation) begin? ~7 days after fertilization
Pre-embryonic Period
The inner cell mass (embryoblast) divides into two cell layers that form a flat disc. What is the anatomical term for this disc? Bilaminar germinal disc (blastodisc)
Pre-embryonic Period
What is the collective term for the membranes formed to mediate the exchange between the uterus and the embryo? Extraembryonic membranes
Pre-embryonic Period
Which membrane forms first and is involved in the formation of blood cells and blood vessels? Yolk sac
Pre-embryonic Period
Which membrane forms a fluid filled sac immediately around the embryo? Amnion
Pre-embryonic Period
Which membrane is outermost and eventually forms the placenta? Chorion
Pre-embryonic Period
What is the organ of exchange between the mother and the embryo? Placenta
Pre-embryonic Period
What 2 layers of tissue contribute to its formation? Fetal: Chorion Maternal: Endometrium
Pre-embryonic Period
What structure initially connects the embryo to the organ of exchange? Connecting stalk
Pre-embryonic Period
What does this initial structure develop into? Umbilical cord
Pre-embryonic Period
What stalk-like structures form from the chorion? Chorionic villi
Pre-embryonic Period
In this organ of exchange (the placenta) do the mother’s blood and the embryo’s blood mix? No
Pre-embryonic Period
What is the common name for this organ of exchange (the placenta)? Afterbirth
http://www-medlib.med.utah.edu/WebPath/PLACHTML/PLAC032.html
Embryonic Period
What process results in the formation of three primary germ layers? Gastrulation
Embryonic Period
What are the three primary germ layers? Ectoderm Mesoderm Endoderm
Embryonic Period
When does the blastocyst become an embryo? During gastrulation (after implantation) 3rd week
Embryonic Period
What type of folding results in the formation of the head and buttocks? Cephalocaudal folding
Embryonic Period
What type of folding results in the formation of the torso? Transverse folding
Embryonic Period
What structures form from the ectoderm? Nervous system Epidermis
Embryonic Period
What inductive action transforms a portion of the ectoderm into a hollow tube which develops into the nervous system? Neurulation
Embryonic Period
What structures form from the mesoderm? Muscle Connective tissue Urinary system Reproductive system Cardiovascular system Lining of body cavities
Embryonic Period
What structures form from the endoderm? Linings of
Digestive tract Respiratory tract Urinary tract
Thyroid, parathyroids, thymus Liver, gallbladder, pancreas
Embryonic Period
What is the process by which organs develop? Organogenesis
Embryonic Period
What are substances that may cause birth defects? Teratogens
Fetal Period
During what time period does the fetal period occur? Week 9 (3rd month) to birth