Basics Of Embryology IIII Flashcards
What germ layers form during gastrulation?
All of them
What germ layer is involved in neurulation
Ectoderm
What germ layer is involved in notochord formation?
Mesoderm
What is the body plan?
Tube within a tube body plan (ectoderm within a endoderm tube)
Neurulation converts the neural plate into a hollow neural tube covered by ___________
Surface ectoderm
The neural tube differentiates into ______________
Brain and spinal cord
What major regions of the brain become apparent before the 4th week?
Forebrain (prosencephalon)
Midbrain (mesencephalon)
Hindbrain (rhombencephalon)
Neurons and glia begin to differentiate from the ____________ of the neural tube
Neuroepithelium
As neurulation occurs, ____________________ detach from the lateral lips of the neural folds and migrate to numerous locations in the body, where they differentiate to form a wide range of structures and cell types
Neural crest cells
2 types of ectoderm
- neural ectoderm
- surface ectoderm
Neural crest cells from the mesencephalon and rhombencephalon regions also give rise to structures in the developing ____________________________
Pharyngeal arches of the head and neck
What structures form from the pharyngeal arches
Bones of the nose, face, middle ear, and neck
Mesencephalon and rhombencephalon neural crest cells form the ______________________________
Dermis, smooth muscle, and fat of the face and ventral neck
Neural crest cells arising from the caudalmost rhombencephalon contribute, along with vagal neural crest cells, to the
Parafollicular cells of the thyroid
Where do neural crest cells migrate out of?
The leading edge of the neural tube
The rhombencephalon neural crest cells also contribute to some of the ________________ ganglia
Cranial nerve ganglia
- specifically neuron and all glial cells in the sensory ganglia of cranial nerves V, VII, IX, and X
- you can tell where the CN come from based on where they emerge in the head
Group of cells that migrate to the same area for a similar function
Placode
CN I arises from the ______________
Olfactory placode
CN II arises from the ________________
Optic cup (the distal end which thickens as the placode-like rudiment of the neural retina)
CN VIII and the vestibulocochlear ganglion arise from the __________
Otic placode
The ________________ gives rise to the cranial component of the parasympathetic division of the autonomic nervous system
Rhombencephalic neural crest cells
-specifically POST GANGLIONIC neurons
The entire cranial component of the parasympathetic division of the autonomic nervous system is formed from ______________
Cranial neural crest cells
What germ layer comprises the pia ad arachnoid mater?
Ectoderm
What germ layer comprises the dura mater
Mesoderm
What kind of cells give rise to the pia and arachnoid mater?
Cranial neural crest cells
What does the dura mater arise from?
Largely or exclusively from head (paraxial) mesoderm
Some cranial neural crest cells invade the surface ectoderm as they migrate away from the neural tube to form ___________
Melanocytes of the skin of the head and neck
These originate from the vagal region and have 3 major contributions
Neural cells
Three major contributions of neural cells
- Outflow tract of the heart (surrounding vasculature of heart)
- Enteric nervous system
- Parafollicular cells of the thyroid
Vagal neural crest cells migrate into the cranial pole of the developing heart, where they contribute to the septum that forms to partition the ___________
Outflow tract of the heart
Vagal neural crest cells migrate more dismally into the gut wall mesenchyme to form neuron, constituting the __________________, that innervates all regions of the gut tube from the esophagus to the rectum
Enteric nervous system
Vagal neural crest cells migrate with those from the caudal rhombencephalon to the pharyngeal pouches, where they contribute to the __________
Parafollicular cells of the thyroid
The peripheral nervous system of the neck, trunk, and limbs includes the following 4 types of peripheral neurons:
- Peripheral sensory neurons
- The cell bodies of which they reside in the dorsal root ganglia
- Sympathetic and parasympathetic autonomic peripheral motoneurons
- Cell bodies of which resides respectively, in the sympathetic and parasympathetic ganglia
All 4 types of peripheral neuron, plus their associated glia, are derived from _______
Neural crest cells
Shortly after somite formation, each somite reorganizes into two subdivisions:
- The epithelial dermamyotome
2. Mesenchyme sclerotome
Formation of the sclerotome, like ingression of cells through the primitive streak and formation of neural crest cells, is another example of ___________
Epithelial mesenchyme transformation
__________ will develop into the vertebrae
Sclerotomes (ventral portion)
Germ layer that makes up sclerotomes?
Mesoderm
What does the dorsal sclerotome form?
Vertebral arch
Two layers of the skin
- epidermis
- dermis
Epidermis germ layer
Surface ectoderm (neural ectoderm)
Germ layer of the dermis
Mesoderm
Mesenchyme
The epidermis is formed mainly by the embryonic ____________, although it is also colonized by melanocytes which are derived from the _______________
- surface ectoderm
- neural crest cells
Dermis of the trunk is a ___________ tissue
Mesodermal tissue
The ventral dermis is derived mainly from the _________ layer of the ___________
- somatic layer
- lateral plate mesoderm
Dorsal dermis is derived from the __________ subdivision of the somites
Dermamyotome
Dermis of the face is formed from ___________
Neural crest cells
Development of bone and muscle occurs within _________ regions of the embryo after the tube within a tube body plan is established during the 4th week of gestation
Mesenchymal
When does bone and muscle formation occur?
Week 4
Two ways that bone formation occurs
- endochondrial ossification
- intramembranous ossification
Endochondrial ossification
- cartilage forms first and bone replaces it
- axial skeleton
- cranial base, limbs
- exception is part of clavicles
Intramembranous ossification
Bone forms directly from mesenchymal cells, no cartilage
-cranial vault and most of the bones of the face
Shortly after formation of the somatic myotome, the myotome splits into a dorsal _______ and ventral ________
- epimere
- hypomere
The epimere forms the _____________, which are innervated by the dorsal ramus of the spinal nerve
Epaxial muscles of the back
The hypomere forms the _________________, which are innervated by the ventral ramus of the spinal nerve
Hypaxial muscles of the lateral and ventral body wall in the thorax and abdomen
Even before neurulation begins, the primordia of the three primary brain vesicles (prosencephalon, mesenchephalon, and rhombencephalon) are visible as broadenings of the ___________
Neural plate
During the 5th week, the prosencephalon divides into the __________________________
Telencephalon and diencephalon
What week does the prosencephalon divide into the telencephalon and diencephalon?
5
The rhombencephalon divides into the _____________
Mesencephalon and the myelencephalon
When does the rhombencephalon divide into the myelincephalon and the metencephalon?
Week 5
Along with the mesencephalon, there are how many brain vesicles?
5
- telencephalon and diencephalon (from the prosencephalon)
- myelincephalon and metencephalon (from the rhombencephalon)
- mesencephalon
The extension of the neural tube caudal to the rhombomeres (small divisions of the hindbrain) constitutes the ___________
Spinal cord
The nervous system of vertebrates consists of two major functional divisions:
- somatic nervous system (skin and skeletal muscle)
- visceral nervous system (glands/organs/smooth muscles)
Another name for the visceral nervous system
Autonomic nervous system
When does lung development occur?
Beginning of week 4
Development of the kings begins with the formation of the ventral outpouching of the ________________ called the ________________
- endodermal foregut
- respiratory diverticulum
The respiratory diverticulum grows ventrocaudally through the ___________ surrounding the foregut
Mesenchyme
On days 26-28, the respiratory diverticulum undergoes a first bifurcation, splitting into right and left ____________
Primary bronchial (or lung) buds which are the rudiments of the two lungs and the right and let bronchi
The proximal end (stem) of the respiratory diverticulum forms the _________
Trachea and larynx
Germ layer making up larynx and trachea
Endoderm
Germ layer of lungs
Endoderm
The heart derives from _________
Splanchnic mesoderm
When do you get first heartbeat
Day 21
Why does the heart beat and continue to beat at day 21?
Its continual beating is required for normal heart development
When does the heart undergo a series of events to separate the pulmonary and systemic circulation at birth
Between weeks 4 and 8
When do blood vessels start to form?
Week 3
What do blood vessels arise from?
Splanchnic mesoderm of the yolk sac wall
Vessels begin to arise in the plan Hingis mesoderm of the yolk space walls from aggregations of cells called __________
Hemagioblasts
From hemagioblasts, two cell lineages arise:
- primitive hematopoetic progenitor cells
- endothelial precursor cells
Where does vasculogensis commence?
In the splanchnic mesoderm of embryonic disc
Where does vasculogenesis continue later on?
Paraxial mesoderm
When does the body folding to produce the gut tube happen?
4th week
The endodermal gut tube created by body folding consists of a blind-ended cranial ________, and blind ended caudal ________, and a midgut open to the yolk sac through the vitelline duct
- foregut
- hindgut
- midgut
When is the pharynx, esophagus, stomach, and proximal duodenum visibly divided
Week 5
The __________ divides into the pharynx, esophagus, stomach, and proximal duodenum
Foregut
The ________ forms the distal duodenum, jejunum, ileum, cecum, ascending colon, and proximal two thirds of the transverse colon
Midgut
The __________ forms the distal third of the transverse colon, the descending and sigmoid colon, and the upper two thirds of the anorectal canal
Hindgut
The ____________ one either side of the dorsal body wall gives rise to three successive nephric structures
Intermediate mesoderm
The intermediate mesoderm, also known as the _________, forms a segmental series of epithelial buds called __________
- nephrotome
- pronephroi
Germ layer for kidney development
Intermediate mesoderm
As these cranial pronephroi regress in the 4th week, a pair of elongated __________ succeeds them, developing in the thoracic and lumbar regions
Mesonephroi
The ________ become the first kidney to function in the embryo, having complete, although simple, ________.
- kidneys
- nephrons
When does the reproductive system develop
6th week
What gives rise to the reproductive system?
Intermediate mesoderm
What is the germ layer that makes up the face
Ectoderm
The skeleton of the head and pharynx is made up of the ____________
Neurocranium and viscerocranium
What is the neurocranium
-the bones that support and protect the brain and sensory organs
What is the viscerocranium
Bones of the face and the pharyngeal arches
What are the divisions of the neurocranium
- Cranial base (bones underlying the brain)
- Cranial vault (bones covering the brain)
- Sensory capsules (bones encapsulating the sensory organs)
Many of the skeletal structures in the head are unusual in that they are formed from __________ rather than from mesoderm, as they are in the rest of the body
Neural crest cells
What is the germ layer for the occipital bone?
Mesoderm (everything else in head is ectoderm )
The external and middle ears arise from the __________________
First and second pharyngeal arches and the intervening pharyngeal cleft, membrane, and pouch
The inner ear develops from ___________________
Ectodermal otic placode
Where does the ectodermal otic placed appear?
On either side of the neural tube at the level of the future caudal hindbrain
What does the ear develop from?
Rhombencephalon
Placodes for eye
Optic sulci
When does the eye develop?
4th week
The eyes appear early in the 4th week in the form of a pair of lateral grooves called the optic sulci, which evaginate from the forebrain neural grooves to form the _________
Optic vesicles
As soon as the distal tip of the optic vesicle reaches the surface ectoderm, it invaginates, transforming the optic vesicle into a goblet-shaped _________ that is attached to forebrain by optic stalks
Optic cup
The adjacent surface ectoderm next to the optic cup simultaneously thinckens to form a _________, which invaginates and pinches off to become a ___________
- lens placode
- hollow lens vesicle
The inner wall of the optic cup gives rise to the ___________
Neural retina
The outer wall of the optic cup gives rise to the thin ____________
Melanin containing pigmented epithelium
Week 4
- neural crest cell migration
- cranial neuropore closes
- caudal neuropore closes
