Human body plan, similarities in humans, human embryos to other life forms...
- Tube within a tube:
- Inner tube - Tube from mouth to anus including respiratory and digestive organs. Outer tube - axial skeleton ( head, neck, trunk ), muscles, and nervous structure.
Bilateral symmetry - Most of left and right half of the body are mirror images of each other.
Dorsal hollow nerve cord - Hollow nerver cord that develops into brain and spinal cord.
Notochord and vertebrae - Notochord is a stiffening rod in the back just deep to the spinal cord. Most of this becomes back bone during development but bits of it become the cores of the discs between the vertebrae.
Segmentation - Outer tube of the body shows evidence of segmentation. Rib cage is made up of segments of ribs, spine made up of segments of vertebrae, nerves branching off as segments of the spinal cord.
Pharyngeal pouches - Pharynx is the throat region. In embryo stage these correspond to the gills on a fish. The pharyngeal pouches develp into structures in the head and neck.