© 2008 Mark Tuttle
EPIBLAST
HYPOBLAST
All 3 germ layers
Disappears to form exocoelomic cyst
Amnioblast
leave behind 2ndary yolk sac
Notochord (migrates from primitive streak)
- induces overlying ectoderm to form neural tube
- becomes nucleus pulposus
Mesoderm
Dura mater
Blood – red and white cells (from yolk sac, liver, spleen, bone marrow)
Connective tissue
Cartilage
Bone
Dermis of skin
Eye – ciliary muscle (controls lens shape)
Muscle – skeletal, cardiac, smooth
Heart
Endothelium of blood & lymph vessels
Ovaries & testes
Spleen
Kidneys
Adrenal cortex
- Paraxial mesoderm
Somitomeres: after 20 pairs formed, become Somites below 7th somitomere
- Pharyngeal arch muscles from somitomeres that become skeletal muscle
Facial expression muscles, Pharynx, Larynx, Muscles of mastication
Somites
- Sclerotome / Somitic mesoderm (ventral):
become loose mass of mesenchyme
Axial skeleton – Vertebrae, Ribs, Sternum, Costal cartilages
- Dermamyotome (dorsal)
o Dermatome: Skin, dermis
o Myotome
 Epaxial (dorsal rami): deep muscles of back
 Hypaxial (ventral rami): limb muscles, tongue, lateral and ventral
body wall muscles
- Intermediate mesoderm
Kidney
Gonads (germ cells move into yolk sac then move back into embryo)
- Lateral plate mesoderm
- Intraembryonic coelom
- Splanchnic
o GI smooth muscles
o Heart, cardiac smooth muscle, cardiogenic mesoderm
- Somatic
o Connective tissue, Blood vessels, Body wall muscles – intercostal mm
- Appendicular skeleton – Clavicle, Scapula, Pelvic girdle, Limb bones
© 2008 Mark Tuttle
Ectoderm
Epidermis, Hair, Nails
Eye lens
Sweat and Sebaceous glands
Mammary glands
Pituitary gland
Olfactory epithelium
Teeth enamel
- Neuroectoderm (forms neural plate which folds to form neural tube)
Central Nervous System (CNS) – brain, spinal cord
Iris, retina of eye
- Neural crest (on either side of neural tube)
Melanocytes
Pia mater – filum terminale, denticulate ligaments
Arachnoid mater
Adrenal medulla
Pharyngeal arch skeletal components - Cartilage, Bone, outer covering
Peripheral Nervous System (PNS) – Sympathetic and Parasympathetic neurons
Ganglia– autonomic, dorsal root; Schwann cells
Sensory neurons of proprioception (awareness of movement & position of parts
of your body)
Cardiac nerves, pulmonary and aortic valve, septum between pulmonary trunk and aorta
Endoderm
Epithelial lining of:
Gastrointestinal tracts
Respiratory tracts
Bladder
Vagina
Thymus
Liver
Pancreas
Thyroid and Parathyroid glands
originally from yolk sac
Extraembryonic splanchnic mesoderm – become blood and blood vessels
mesodermal wall of secondary yolk sac, wall of chorion
To get CSF, lumbar puncture needle pierces in order:
Supraspinous ligament
Interspinous ligament
Ligamentum flava
Epidural space
Dura mater
Arachnoid mater
CSF is in subarachnoid space