Anatomy, Bone Structure, and Evolution Lecture Notes

Vocabulary terms covering anatomical positions, bone types and structures, and the principles of evolution and cladistics based on lecture notes.

Anatomical position

standing straight, feet slightly apart, thumbs pointing away from body

Superior/cranial

toward the head

Inferior/caudal

toward the feet

Dorsal

toward the back

Ventral

toward the front

Anterior

front of the body

Posterior

back of the body

Medial

toward the midline

Lateral

away from the midline

Proximal

closer to the point of attachment

Distal

farther from the point of attachment

Median/midsagittal plane

cuts body into equal left/right halves

Lateral plane

cuts body into unequal left/right sides

Transverse plane

cuts body into top/bottom sections

Dorsal body cavity

contains brain and spinal cord

Ventral body cavity

contains thoracic, abdominal, pelvic organs

Cranial cavity

holds the brain

Vertebral cavity

holds the spinal cord

Thoracic cavity

holds heart and lungs

Abdominal cavity

holds digestive organs

Pelvic cavity

holds bladder and reproductive organs

Flat bone

thin, plate-like bone (ex: scapula)

Short bone

cube-shaped bone (ex: wrist bones)

Long bone

bone with a long shaft (ex: femur)

Irregular bone

odd-shaped bone (ex: vertebrae)

Sesamoid bone

small, round bone inside a tendon (ex: patella)

Epiphysis

end of a long bone

Diaphysis

shaft (long part) of a bone

Epiphyseal plate

growth plate (cartilage) between epiphysis and diaphysis

Articular cartilage

cartilage covering bone ends at joints; cushions and reduces friction

Medullary cavity

hollow space inside the diaphysis; holds bone marrow

Hematopoesis

production of blood cells in red bone marrow

Periosteum

tough outer covering of bone; site of muscle attachment and repair

Spongy bone

bone with open spaces (trabeculae); found at ends of bones

Compact bone

dense, solid bone; makes up the shaft

Osteoclast

cell that breaks down bone

Osteoblast

cell that builds new bone

Trabeculae

little beams forming the lattice structure of spongy bone

Osteon

cylinder-shaped unit of compact bone

Lamellae

concentric rings of bone matrix making up an osteon

Haversian system

central canal in an osteon carrying blood vessels and nerves

Canaliculi

tiny channels connecting osteocytes so they can get nutrients

Perforating canal

channel connecting Haversian canals to each other, runs perpendicular

Evolution

change in allele frequency (or speciation) in a population over time

Five fingers of evolution

genetic drift, sexual selection, mutations, gene flow, natural selection

Natural selection

organisms with helpful traits survive and reproduce more; drives adaptation

Artificial selection

humans breed organisms for chosen traits

Homologous structure

similar structure due to common ancestor (ex: human/whale/bat arm bones)

Analogous structure

different structure, same function, not closely related (ex: bird wing and insect wing)

Vestigial structure

leftover structure no longer used (ex: human tailbone, whale leg bones)

Fitness

an organism's ability to survive and reproduce in its environment

Adaptation

an inherited trait that helps an organism survive and reproduce in its environment

Dichotomous key

step-by-step yes/no questions used to identify or classify organisms

Cladogram

branching diagram (family tree) showing evolutionary relationships

Leaf

tip of a branch on a cladogram; represents one species

Node

branch point on a cladogram; represents a common ancestor

Most recent common ancestor

the lowest/most recent node shared by two leaves

Outgroup

the leaf that shares the fewest nodes with the rest of the tree; most distantly related