General embryology Flashcards
List the three pre-embryonic stages of development
- Zygote (fertlised ovum)
- Morula
- Blastocyst
When does a blastocyst become an embryo?
Day 10-12
When does an embryo become a fetus?
8 weeks
Where does the trophoblast arise from? What do these cells form?
From the outer layer of the blastocyst, and they form a large part of the placenta
What two cavities form from the inner cell mass of the blastocyst? What divides these cavities?
The ambion, and the yolk sac, either side of the embryonic plate.
What arises from the embryonic plate?
The ectoderm and endoderm
What does the mesoderm arise from?
The ectoderm
Other than the mesoderm, what forms from the ectoderm early on?
The neural tube
What are the terminal products of the ectoderm?
Skin, appendages
Neural tissues
What epithelia are formed from ectoderm? What do other epithelia arise from?
Skin, lining of the mouth and anus, nostrils, sweat glands and hair follicles.
Other epithelia arise from the endoderm.
What part of the tooth arises from ectoderm?
What part of the tooth arises from neural crest cells?
Tooth enamel - ectoderm
Dentine and cementum - neural crest cells
List the ten end products of neural crest cells
- Parafollicular (C) cells of the thyroid
- Chromaffin cells of the suprarenal medualla
- Melanocytes
- Post root ganglia of spinal nerves and the corresponding ganglia of cranial nerves
- Autonomic ganglia
- Neuroglia, Shwann cells
- Meninges
- Bones of the skull and face
- Sclera and choroids of eye
- Dentine and cementum of teeth.
What major embryological structure does gastrulation form?
Gastrulation creates a mesodermal layer between the endoderm and ectoderm.
What forms at the same time that gastrulation is occuring
The neural tube
What extends beneath the neural tube from the base of the head to the tail?
The notochord
What lies either side of the neural tube? How are these cells referred to in mammals?
Thick bands of mesodermal cells, the “paraxial mesoderm”, or the “unsegmented mesoderm”
What two things begin to form as the primitive streak regresses?
- The neural folds begin to gather at the centre of the embryo
- The paraxial mesoderm begins to separate into blocks of cells called somites
Somites are transient structures. How do they contribute to embryonic development?
They are extremely important in organizing the segmental pattern of vertebrate embryos
For what cells types do somites control migration paths?
Somites determine the migration paths of neural crest cells and spinal nerve axons
What 5 groups of end products arise from somites?
Somites give rise to the cells that form the vertebrae and ribs, the dermis of the dorsal skin, the skeletal muscles of the back, and the skeletal muscles of the body wall and limbs.
What three embryonic structures arise from the mesoderm?
- the sclerotome
- The dematomyotome
- The intermediate cell mass
What is the sclerotome?
The part of each somite in a vertebrate embryo giving rise to bone or other skeletal tissue
What is the dermatomyotome
An epithelial cell layer constituting of the dorsal part of the somite lying under the ectoderm
What four structures arise from the intermediate cell mass?
- Pronephros
- Mesonephros
- Metanephros and associated ducts
- The cortex of the suprarenal gland.
What is the pronephros? What stucture does it eventually become?
The most basic of the three excretory organs that develop in vertebrates, corresponding to the first stage of kidney development. … It is a paired organ, consisting of a single giant nephron that processes blood filtrate produced from glomeruli or glomera- large embryonic glomeruli.
What is the mesonephros? What is it replaced by?
Either member of the second and midmost of the three paired vertebrate renal organs that functions in adult fishes and amphibians but functions only in the embryo
It is replaced by the metanephros
What is the metanephros?
Either member of the final and most caudal pair of the three successive pairs of vertebrate renal organs that functions as a permanent adult kidney
What eventually arises from the endoderm?
The gut and lungs, including liver and pancreas
What does the spleen arise from?
The spleen arises from a proliferation of mesenchyme within the dorsal mesentary, overlying the dorsal pancreatic endoderm
What is mesenchyme?
A loosely organized, mainly mesodermal embryonic tissue which develops into connective and skeletal tissues, including blood and lymph
What is the difference between mesoderm and mesenchyme?
Mesoderm is one of the three germ layers of bilaterally symmetrical animals while mesenchyme is an undifferentiated tissue found in embryonic true mesoderm
List five structures in the embryo that change at birth
- The umbilical vein
- The ductus venosus
- The foramen ovale
- The ductus ateriosus
- The umbilical arteries
What does the umbilical vein become?
The ligamentum teres
What does the ductus venosus become? Where is this structure found?
The ligamentum venosum (within the liver, between segments III and IV
What becomes of the foramen ovale?
It closes
What does the ductus ateriosus become?
The ligamentum ateriosum
What do the umbilical arteries become?
The medial umbilical ligaments
