Lecture 10 - Embryology I Flashcards
What is the structure of a blastocyst?
Blastocoel cavity
Trophoblast around outside
Inner cell mass
Describe the initial stages of development
Fertilisation in the Fallopian tube
Morula: 3 days
Blastocyst: 4 days
What does the trophoblast become?
Extraembyronic tissue
What does the inner cell mass become?
Epiblast and hypoblast
When does the embryo implant?
5-10 days
What is the bilaminar disc?
This is the epiblast and hypoblast
NB Gastrulation has yet to occur
Describe the process of gastrulation
Primitive streak appears on epiblast
Thickens –> primitive groove
Cells migrate medially, then down through the primitive node
Endoderm forms, pushing away hypoblast
Cells migrate on top of endoderm to form mesoderm
Cells left form the ectoderm
What is the fate of the different cells types in the bilaminar embryo?
Part of the epiblast: embryo
Some epiblast + hypoblast : extra embryonic tissue
How does the notochord form?
Cells migrating through primitive node and anterially form the mesodermal notochord
What are the derivates of ectoderm?
Skin
Nervous system
What are the derivate a of mesoderm?
Pleura Dermis Skeleton Haematopoetic tissue Vasculature Heart Walls of organs Muscles
What are the derivatives of endoderm?
Endothelium of hollow organs
Gastrointestinal tract
Respiratory endothelium
Describe the formation of the nervous system
Aka neurulation
Mesodermal notochord induces overlying ectoderm to form neural plate
Neural groove forms on ectoderm
Ectoderm raises up on the sides, and meets in the middle to form the neural tube
Neural crest cells migrate and go on to form many types of structures
What are the derivatives of neural crest cells?
Dentine Bones and cartilage of face Melanocytes Sympathetic and parasympathetic ganglia Posterior root ganglia Enteric ganglia Schwann cells
Describe what happens to the neural tube once it forms
Vesicles form, giving rise to he brain and the spinal cord
What gives an identity to the various segments of the neural tube?
HOX genes
What are the divisions of the mesoderm?
Paraxial (somatic and splanchnic)
Intermediate
Lateral
What is the fate of paraxial mesoderm?
Skeleton
Muscles
Dermis
What is the fate of the intermediate mesoderm?
Urogenital system
What is the fate of lateral mesoderm?
Heart and blood
Pleura
Wall of gut and respiratory system
Body wall
Describe what happens to the paraxial mesoderm
Somiteres (swellings) form down the sides of the neural tube
Once there are 20 somiteres, the eight pair separates to become a pairs of somites.
This then continues down the axis
What happens to the first seven somiteres?
They never go on to form somites
What happens to a Somite?
Divides up into:
Dermomyotome
Sclerotome
What becomes of the sclerotome?
The skeleton
What becomes of the dermomyotome?
Dermatome: dermis
Myotome: muscle
Differentiate between lateral and medial myotome
Lateral: limb & ventrolateral body wall muscles
Medial: intrinsic back muscle
Differentiate between lateral and medial dermatome
Both dermis
Differentiate between lateral and medial sclerotium
Medial: vertebral body, intervertebral disk, proximal rib
Lateral: vertebral arch, pedicle, distal rib
From what does the appendicular skeleton form?
Lateral plate of mesoderm
What does the blastocoel go on to form?
Yolk sac
Where is the amniotic cavity?
Above the epiblast cells and under the trophoblast cells
