Question

MCAT Tutorial: The Skeletal System

Answer 1

\({\bf{Functions~of~the~Skeletal~System:}}\) structure, protection, levers for muscles, blood formation, storage of fat, calcium, phosphate ions, fat, minerals, growth factors

\({\bf{Structure~of~Bone~Tissue:}}\)
- three types of connective tissue: compact bone, spongy bone, cartilage
- osseus tissue: composed of osteoclasts, osteoblasts, osteocytes
> osteoclast: break down old bone
> osteoblasts: create new bone from osteoid --> hardens into hydroxyapatite
> osteocytes: mature form of osteoblast, does not make new bone

Compact Bone:
- basic unit: osteon
- osteon is made of central canal surrounded by lamellae
- lacunae: storage sites of osteocytes
- canaliculi: connect the lacunae
- perforating/Volkmann's canals: supply blood to bone

Spongy Bone:
- light, porous
- found at the ends of long bones
- trabeculae: supporting rods of spongy bone

Cartilage:
- connective tissue, elastic
- has no nerves/blood vessels
- nourished by perichondrium

Answer 2

\({\bf{Bone~Types:}}\)
- long bones*: make up large appendages like femur, the most important one to study for the MCAT
- short bones: short appendages like wrist or ankles
- flat bones: skull, ribs, scapulae, sternum
- irregular bones: vertbrae
- sesamoid bones: bonds within the tendons/patella

\({\bf{Long~Bone~Structure:}}\)
- diaphysis: middle part of the bone; compact bone
- epiphyses: ends of the long bone; spongy bone
- medullary cavity: interior of the long bone
> red marrow: fills the medullary cavity during fetal stage, hematopoieic
> yellow marrow: fills the medullary cavity during adult stage, stores adipose
- periosteum: lines the outer surface of bone, supplies blood/nerve tissue
- endosteum: lines medullary cavity
- epiphyseal plate: site of growth

Answer 3

\({\bf{Ossification:}}\) growth of bones via secretion of tissue by the osteoblasts
- intramembranous ossification: forming bone from connective tissue, ex. mandible and top bones of skull
- endochondral ossification: replacement of cartilage with bones
- osteolysis: breaking down bone by osteoclasts
> regulated by calcitonin and parathyroid [see my tutorial on the endocrine system]

\({\bf{Joints:}}\)
- fibrous: fibrous connective tissue, not movable, ex. sutures
- cartilaginous: semi-movable, cushioned with cartilage, ex. joints between vertebrae
- synovial joints: movable, fluid-filled [most joints are synovial] ex. knee and elbow joints
> surrounded by synovial membrane + fibrous joint capsule
> joint capsule: resists tension
> synovial membrane: secretes fluid to lubricate joints
> articular cartilage: reduces friction

ligaments: connect bone to bone
tendons: connect muscles to bones
bursae: fluid filled capsules between ligaments and bones

Answer 4

ugh I just realized that first image was copyrighted so just to be on the safe side here's another image of the compact bone structure

Answer 5

Anyway, that's the end of my tutorial, I hope it was a helpful resource. Source material is the 2nd Edition Barron's Prep book for the new MCAT

Answer 6

This is amazing. I love the image you used to start the tutorial!