Embryology week 17 Flashcards
What are teratogens + examples
Agents that may cause cogenital anomalies when the embryo is exposed to them during the 4 - 8 weeks
Rubella virus, thalidomide , Warfarin
When does the embryo fold
Fourth week
Name the three phases of embryonic development
Growth
Morphogenesis
Differentation
Explain what happens in the 3 phases of human development
Grwoth- cell divison
Morphogenesis- development of the shape of the organ and whole body
Differentiation(maturation) - the formation of tissues and organs that are capable of performing specialsied tissue functions -
When the embryo folds what exaclty folds
cranial ends, caudal ends and sides
Explain what happens when the head folds
-Neural folds
-Septum transversum
- The neural folds have thickened to form the primdorium of the brain
-Septum transversum, primodrial heart and move onto the ventral surfaceof the embryo
Where does the foregut lie
- Between the brain and heart
What happens to the endoderm of the umbilical vesicles during head folding
- Endoderm of the umbilical vesicle is incorporated into the embryo as the foregut
What seperates the foregut from the stomodeum of the mouth
Oropharyngeal membrane
What changes occur to the septum transversion in relation to the heart before and after head folding occurs
Before the septum transversum lies cranially to the heart but after it lies caudally
Explain what happens to the tail during the folding of the embryo
The tail folds and extends over the cloacal membrane, which will later become the anus
What does the hindgut develop into
colon and rectum
How is the cloaca formed starting from the hindgut
-Hindgut expands to form the cloaca
Explain how the primitive streak changes before and after folding
Before folding the primtive streak is cranial but after folding it is moves caudal
During folding where does the connecting stalk move
To the ventral surface of the embryo
During folding what is the allantois incorporated into
- Emrbyo
What does the folding of the sides of the embryo produce
- Right and left lateral folds
When is the midgut formed
When the embryo folds in the horizontal plane
During the embryo folding in the horizontal plane, What is the endoderm germ layer incorporated into
- `
incorporated into the embryo as the midgut
What does the midgut have a wide connection to
umbilical vesicle
What are the neural crest cells derived
neuroectoderm
What are the ectoderm derivatives
- central and preipheral nervous systes
-glands
-
Which structures are formed from the neural crest cells
- Autonomic ganglia
-Muscle
What are the characteristsics of mesoderm
-Connective tissue
-Bone
- Cartilage
What are the characteristics of the ectoderm
Central and peripheral nervous system
pituitary glands
Explainn the structure of the embryo on the fourth week and how many somites does it contain
- Embryo is almost straight
-Contains 4-12 somites
What are the openings of the neural tube called
- rostral(head end)
-caudal( tail end)
What completes the development of the central nervous system
neurpores
When do the first two pharyngeal arches appear
fourth week
What does the first pharyngeal arch form
lower jaw
In the 4 week (26 days) how many pairs of pahryngeal arches are present
-3
When is the upper limb buds recognized
day 26 ( 4th week)
What are the ortic pits
- primordia of the internal ears
What does the mesonephric ridges form
Kidneys
What happens during the 5th week of development
- Head grows more
-2 pharyngeal arches form
-Mesoneophric ridges form
What happens in 6th week
- hand plates start to develop
-Development of the lower limb
-Spontaneous movements
What happens in the 7 th week
- Ossification of the bone starts in the upper limb
What happens in the 8th week
- Head is bigger, half the size of the embryo
-Neck region is established
-Eyelids developW
When does embryonic age begin
Fertilisation
what is used to estimate the embryonic age
- They day when fertilisation occurs
