Embryology Flashcards
What is the definition of “cytology”?
Study of the fundamental units of life
What are the two characteristics of life?
Metabolism and reproduction
Somatic cells are responsible for…
metabolism
Sex cells (sperm and egg) are responsible for…
reproduction
What is considered the basic functional unit?
a cell
What is a somatic cell?
any cell of a living organism other than the reproductive cells
How does stability work in regard to the cellular membrane?
- It is due to the phospholipid bilayer
- The hydrophilic (water-loving) head faces outward towards the watery environment while the hydrophobic (water-fearing) tails face each other
- The cholesterol also helps stabilize by preventing the creation of fatty acid chains
How does mobility work in regard to the cellular membrane?
- Mobility allows for the cellular membrane to change shape which helps with cell division, movement, and endocytosis
- Proteins are also constantly moving in the cellular membrane creating channels for ions to pass through, transporting molecules, and being receptors for signals
What does the cellular skeleton do?
Made up of microfilaments and microtubules to hold shape
What does the nucleus do?
Contains DNA and genetic material (chromosomes), nucleolus is also in this area and it produces ribosomes
What does the rough endoplasmic reticulum do?
HAS ribosomes attached to it and transports material
What does the smooth endoplasmic reticulum do?
Does NOT have ribosomes attached to it and transports material
What does the Golgi apparatus do?
Receives proteins from endoplasmic reticulum and forms them into something the cell can use
What do centrioles do?
Organizing microtubules that serve as the cell’s skeletal system
What do lysosomes/peroxisomes do?
Lysosomes degrade molecules and peroxisomes convert H2O2 into water and oxygen
What do the mitochondria do?
These are the powerhouse of the cell and create ATP (energy).
They aid in respiration and energy production and contain DNA
Describe the stages of mitosis (the process from diploid to diploid).
- Interphase - preparation for mitosis
- Prophase - Chromosomes condensed and visible
- Metaphase - Chromosomes in the middle of the cell
- Anaphase - Sister chromatids pulled apart by spindle fibers
- Telophase - Chromosomes on opposite ends, two nuclei forming
- Cytokinesis- The cytoplasm of the cell divides, and two identical sets of chromosomes formed (two daughter cells)
What cells go through mitosis?
Somatic cells
What cells go through meiosis?
Sex cells
What is a diploid cell or organism?
An organism or cell contains two complete sets of chromosomes, one from each parent
What is a haploid cell or organism?
An organism or cell that contains just one set of chromosomes
What happens when sperm and egg merge?
They create a diploid zygote with a complete set of chromosomes, half from each parent
How long does it take for an egg to form versus a sperm cell?
Egg - 14 days
Sperm - 64 Days
Describe the steps in meiosis reproduction…
Meiosis 1
1. Prophase 1: chromosomes condense, and homologous chromosomes (pairs of chromosomes, one from each parent) come together
2. Metaphase 1: chromosomes align at the center
3. Anaphase 1: chromosomes are pulled towards opposite ends of the cells
4. Telophase 1 and Cytokinesis: cytoplasm divides creating two cells
Meiosis 2
1. Prophase 2: new spindles form in each new cell
2. Metaphase 2: chromosomes align at metaphase plate
3. Anaphase 2: sister chromatids separated and moved to edge
4. Telophase 2 and Cytokinesis: chromosomes decondensed and cytoplasm divides
What happens during the first week of embryonic development?
- Fertilization
- cleavage: equal distribution of cytoplasm from 2 to 8 cells
- mainly replication - Blastocyst
- unequal distribution of cytoplasm
- the start of differentiation
Cleavage (single-cell zygote dividing - mitosis) –> Morula (solid ball of cells) –> Blastocyst –> Implant Blastocyst in endometrium at day 6 with help of trophoblast cells
What happens during the second week of embryonic development?
- Implantation
- trophoblast cells invade the endometrium and help to implant the blastocyst
- trophoblast start to recruit cells for blood vessels to form the placenta - Inner cell mass develops into epiblast and hypoblast
*30% of blastocysts fail to implant in the 1st 2 weeks
What is the difference between epiblast and hypoblast?
Epiblast: forms tissues and organs
- a layer of cells on the dorsal side of blastocyst
- can form into any cell type in the body
- give rise to ectoderm, mesoderm, and endoderm
Hypoblast: supports developing embryo
- layer of cells on the ventral side of blastocyst
- form the yolk sac and amnion
What happens during the third week of embryo development?
- Formation of the placenta
- Gastrulation: when the epiblast glides against the hypoblast it forms 3 germ layers
- Ectoderm: forms the skin and nervous system
- Mesoderm: forms the muscles, bones, and circulatory system
- Endoderm: forms the lining of the digestive and respiratory systems, and makes up organs like the liver and pancreas - Formation of the notochord: start EMBRYO phase
What is the notochord?
A rod-like structure for the development of the axial skeleton that also helps in the creation of the neural tube
What happens during the fourth week of embryonic development?
- Establishment of body planes
- Formation of somites: mesoderm, notochord as the axis
- somites expand fast and results to the folding of ectoderm to form the neural tube
- the dorsal somite gives ride to the sclerotome and dermomyotome
True or False: muscles and bones develop independently and have no origin or insertion at the beginning
True
The sclerotome is located on the _____ side of the somite.
ventromedial
The dermomyotome is located on the ____ side of the somite
dorsolateral
Somites are formed by the _____.
Mesoderm
The neural tube is formed by the ______.
Ectoderm
Where does the closure of the neural tube initiate and at what point?
At the cervical region at week 4
What happens when the caudal neuropore does not close? (opening at the end of the developing neural tube)
Spina bifida
What happens when the cranial/ rostral neuropore does not close? (opening at the top of the developing neural tube)
Acephaly
Does the neural tube come from the CNS or PNS?
CNS
Does the neural tube have motor or sensory neurons?
Motor
Describe the motor neurons in the neural tube…
- the somatic axons expand outwards to somites
- visceral motor axons expand to visceral motor ganglia
Does the neural crest originate from the CNS or PNS?
PNS
Describe the sensory neurons in the neural crest…
- somatic sensory neurons: axons expanding into both the neural tube and somites
- autonomic nervous system: visceral motor ganglia
What limb is formed first in the fetus?
Upper
Myotomes and dermatomes change with _______.
rotation of the limbs during development
An embryo is almost fully formed at ___ weeks.
9
During development, the upper extremity and lower extremity can move into what positions?
Upper: anatomic position - still segmental distribution
Lower: fixed-torsional alignment
True or false: dermatomes have huge variations among the population and even in right and left in the same individual?
True
What are the five critical stages of development?
- Week 1: fertilization and formation of blastocysts
- Week 2: implantation and formation of epi/hypoblast
- Week 3: formation of placenta and gastrulation - EMBRYO
- Week 4: complete blue prints, primitive organs nonfunctional
- Week 9: FETUS, primitive organs, partially functional
What are the four types of tissues?
- Muscle
- cardiac
- skeletal
- smooth - Epithelial
- skin - Nerve
- brain
- spinal cord
- nerves - Connective
- tendons
- bone
- fat
