Embryology Flashcards
What is neurulation
Process in which the neural tube forms
When does neurulation take place
Week 3-4
What will the neural tube later become
CNS: Brain, spinal cord, meninges
As well as part of the bones that surround them
What is gastrulation and when does it take place?
Week 3
The three primary germ layers (ectoderms, mesoderm, endoderm) form and start becoming different types of tissue
What will the ectoderm differentiate into
Nervous system and skin
What will the mesoderm become
Connective tissue, bone , muscle, urogenital organs, pleura, peritoneal linings of the body cavity
What will the endoderm eventually become
Lining of the internal organs such as GIT and lining of the airways
What structure induces neurulation
Notochord
What will the notochord eventually develop into
Nucleus pulposus of the intervertebral disc
What does the neural tube come off of
Ectoderm
What happens at the end of week 3 related to neurulation
The lateral edges of the ectoderm become more elevated and will form the neural fold.
The depressed mid-region is called the neural groove.
The whole thing is referred to as the neural plate
How does neurulation advance
Both cranially and caudally
It starts from the mid-region
This means that at the end of neurulation, the cranial end will give rise to the brain
Caudally will be the spinal cord
How is the neural tube formed
Fusion of neural folds together
Starts in the middle and goes both cranially and caudally
How is a neural crest formed?
During neurulation as the neural tube forms, some of the ectodermal cells from the tube migrate form several layers of cells called the neural crest
What will the neural crest give rise to
Structures that work very closely with CNS
This includes the peripheral nervous system spinal and cranial nerves and their ganglia
Autonomic nervous system ganglia
E.g
Schwann cells, Pigment cells, adrenal medulla, bony skull, meninges, dermis
Sensory (dorsal root) ganglia
CN 5,7,9,10
What will the remaining ectoderm after neurulation become
Skin
What does the spinal cord of the neural tube become
Spine
What does the rhombencephalon of the neural tube become
Pons
Cerebellum
medulla
What does the mesencephalon of the neural tube become
Midbrain
What does the prosencephalon of the neural tube become
Cerebrum
Thalamus
Further divisions of the prosencephalon, mesencephalon and rhombencephalon
What makes up the tri laminar disc composed of?
Ectoderm
Mesoderm
Endoderm
By what week of embryonic development can the three primary brain vesicles be identified?
By the end of week 5
Embryonic development of the ventricles
Telencephalon- Lateral ventricles
Diancephalan- Third ventricle
Metencephalon- Upper part of the 4th ventricle
Myelencephalon- The lower part of the 4th ventricle
What is spina bifida?
Failure of the tube to close in the spinal cord
What is anencephalus
Failure of the tube to close in the cephalic region
What layer of the trilaminar disc are the kidneys derived?
Intermediate mesoderm.
What are the names of the 3 paired kidneys that develop in the embryo?
- Pronephros.
- Mesonephros.
- Metanephros.
What does the mesonephros form?
The mesonephric ridge and duct.
What does the mesonephric duct form in the male?
The epididymis, vas deferens, seminal vesicles and ejaculatory duct.
What does the ureteric bud form?
The ureters, collecting duct, major and minor calyces and the renal pelvis.
What does the Müllerian duct form in females?
The uterine tubes, uterus, cervix and proximal 1/3 of vagina.
What is the cloaca divided into?
- Anorectal canal.
- Urogenital sinus.
What are the 3 parts of the urogenital sinus?
- Upper part.
- Pelvic part.
- Phalic part.
What part of the urogenital sinus is the bladder formed from?
The upper part.
What does the pelvic part of the urogenital sinus form?
The prostatic and membranous urethra.
What does the phalic part of the urogenital sinus form?
The penile urethra.
What part of the trilaminar disc are the bladder and urethra formed?
The endoderm.
What layer of the trilaminar disc forms the male and female genitalia?
Intermediate mesoderm.
What is the indifferent stage?
When the Wolffian and Müllerian ducts are both present. It is impossible to tell the sex of the embryo.