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What are the 3 phases of human embryology
- conceptus - fertilisation to 3 weeks
- embryo - 3 weeks to end of 8 weeks
- fetus - 3rd month to birth
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what is special about the first cell divisions following conception
the cells don't grow between divisions - why it is called cleavages
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what is the morula
the ball of cells, similar in appearance to a mulberry, formed from the initial cleavages following conception
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how is the blastocyst formed
cells from the morula move to the outside of the ball, forming a cavity
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what 2 cell types make up the blastocyst
- tropoblast - cells on the outside
- inner cell mass (embryonic stem cells)
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what does the tropoblast give rise to
extraembryonic structures
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what does the inner cell mass differentiate into
the epiblast and the hypoblast
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what is the embryonic disk
the 2-cell layer disk that forms between the epiblast and the hypoblast
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 which becomes crainial and caudal from this structure
the part that the primitive groove does not touch is cranial.
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what do the first, and then second and third cells that migrate in from the epiblast, through the primitive groove, become
- first - endoderm
- second - mesoderm
- third - ectoderm
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what does the endoderm give rise to
lung, liver, stomach, intestine, colon, pancreas, bladder, and thyroid
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what does the mesoderm give rise to
skeletal muscles, smooth muscle, blood vessels, bone, cartilage, joints, connective tissue, endocrine glands, kidney cortex, heart muscle, urogenital organ, uterus, fallopian tube, testicles and blood cells from the spinal cord and lymphatic tissue
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what does the ectoderm give rise to
epidermal cells of skin, central nervous system, peripheral nerves
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what is gastrulation
how the 3 primary germ layers (and the primitive streak) are formed
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what are the origins of the following structures?
- dermis
- ovaries
- axial skeletal elements
- kidneys
- muscles in the limbs
- bones in the limbs
- dermis - dermatome (paraxial mesoderm)
- ovaries - intermediate mesoderm
- axial skeletal elements - paraxial mesoderm
- kidneys - intermediate mesoderm
- muscles in the limbs - paraxial mesoderm
- bones in the limbs - lateral mesoderm
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which part of the primitive gut forms the stomach
the foregut
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what is the function of the notochord
specifies the midline of the embryo
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which germ layer does the neural tube form from
the ectoderm
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where do neural crest cells come from
the ectoderm - the cells that cinch together to form the neural tube
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what drives embryonic folding
the fact the the cells of the embryonic disk proliferate at a higher rate than those of the yolk sack/other extra-embryonic structures
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what 3 structures can the mesoderm be divided into
the paraxial, intermediate and lateral mesoderm
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what does the paraxial mesoderm become (what does it differentiate into and what does that give rise to.)
- the somites, which differentiate into the sclerotome and the dermamytome, which further differentiates into the dermatome and the myotome
- dermatome - the dermis
- myotome - certain muscles (muscles of the limbs)
- sclerotome - axial skeletal elements
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what does the intermediate mesoderm give rise to
- the urogenital system
- - gonads
- - kidneys
- - respective duct systems
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what are the roles of the pronephros and mesonephros and uretic bud
- pronephros will just degenerate eventually
- mesonephros function as the embryonic kidney
- uretic bud will become the adult kidney
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what does the lateral mesoderm split into
- the somatic (or parietal) and splanchnic (or visceral)
- gives rise to the bones of limbs, heart and the vasculature and the wall of the gut
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how does vasculogenesis occur
- assembly of blood vessels from mesodermally derived cells
- endoderm signals to overlying mesoderm, causing cells to cluster to form hemangioblasts
- cells on the outside of hemangioblast become angioblasts and the ones on the inside become haematopoetic stem cells
- angioblasts mature into the endothelial cells
- haematopoetic cells give rise to the first blood cells
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explain angiogenesis
- formation of blood vessels from existing vasculature
- hypoxic tissue will the secrete VEGF-A, which will be detected by cells of the blood vessel, causing them to grow in the direction of the hypoxic tissue
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how does the art form
two endocardial tubes fuse, and will begin to swell and twist to form the 4 chambers of the heart
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what are the 2 ends of the endodermal tube reffered to as
buccopharyngeal membrane at the caudal end and cloacal at the caudal end
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label A B and C
- A - intermediate mesoderm
- B and C - lateral mesoderm
- B - somatic (peripheral)
- C - splanchnic (visceral)
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what region of the gut does the stomach form from
the foregut
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describe the formation of the stomach
the dorsal region of the stomach grows faster, causing curvature, while it is growing, the stomach rotates 90 degrees clockwise so that the dorsal region ends up at the left and the ventral part becomes
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what is the respiratory diverticulum
- the bud that forms on the endoderm that grows to form the lungs
- it first becomes the trachea, which will split into the bronchi, then into bronchial buds (the lobes of the lungs - 3 right and 2 left)
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what are the equilibrium potentials of K+ and Na+
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is Vm is greater than EK+ what willl happen
K+ will flow out of the cell
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what does the nernst equation tell us
when the equilibrium of an ion will occur
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equation for driving force
DF = Vm - E ion
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what does the goldman-hodgkin-kaatz equation tell us
- predicts the membrane potential, based on the concentration of ions on either side of the membrane, as well as the permeability of the membrane to these ions
- - does not consider driving force - assumes ions move at the same rate
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concentration vs osmolarity
concentration describes the number of a particular molecule dissolved in a volume of solution while osmolarity describes the total number of dissolved particles in the solution
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role of the anterior vs posterior pituitary
- posterior secretes oxytocin and antidiuretic hormone (vasopressin)
- anterior releases tropic hormones - which are hormones that signal to second order endocrine glands
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how does the hypothalamus communicate to the pituitary glands
neurosecretory cells in the hypothalamus release neurohormones into the blood vessels that will drain into the pituitary stalk, and then to the anterior pituitary, causing it to secrete tropic hormones. It will communicate with the posterior pituitary directly through neuronal communication.
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