A&P Unit 3: Skeletal System

what is the function of the skeletal system?

support, protection, production of blood cells, storage of inorganic materials

how are bones classified?

shape

what are the classifications of bones (+ examples)?

1. long (femur)

2. short (wrist)

3. flat (pelvic)

4. irregular (vertebrae)

5. sesamoid (knee cap/patella)

what is the epiphysis?

expanded portion at the end of the bone that forms the joint

what is the epiphyseal disk?

the growth plate (thin line of cartilage)

what is the diaphysis?

the shaft of the bone

what is the medullary cavity?

the hollow camber in the center of the diaphysis

what is spongy/cancellous bone?

lighter bone that is found in the epiphysis

what is compact bone?

dense, tightly packed bone that surrounds the entire bone for strength and protection

what is the periosteum?

tough exterior of the bone that is vascular and nerve-covered

what is the endosteum?

membrane of osteoblasts on the walls of the medullary cavity

what is articular cartilage?

layer of hyaline cartilage on the epiphysis

what is red marrow? where is it found?

1. forms red and white blood cells and platelets

2. flat bones and epiphysis of long bones

what is yellow marrow? where is it found?

1. stores fat

2. diaphysis

what is a perforating/Volkmann’s canal?

horizontal canals that connect central canals in compact bone

what is a central/Haversian canal?

vertical canals with blood vessels and nerves in compact bone

what is an osteon?

a circular unit of bone that surrounds a central canal

what makes up an osteon?

calcified rings of lamella

what are triabecula?

plates of bone in spongy bone that make it lighter

what are canaliculi

canals between osteocytes in spongy and compact bones

what are osteoblasts?

bone building cells which deposit Ca and P into dense collagen framework and eventually become osteocytes

what are osteoclasts?

large, multi-nucleated cells that secrete acid to break down bone matrix

what is the purpose of osteoclasts?

help with releasing Ca and P into the bloodstream, bone remodeling, and resorption

what occurs when there is too much calcium in the bloodstream?

thyroid gland senses and releases calcitonin which tells osteoblasts to pull Ca into bones

what occurs when there is not enough calcium in the bloodstream?

parathyroid gland senses and releases parathyroid hormone which tells osteoclasts to break down bone

what type of bone does intramembranous ossification form?

flat bone

what does intramembranous ossification do?

changes mesenchymal (undifferentiated) tissue into bone

what are the steps to intramembranous tissue?

1. layers of undifferentiated connective tissue appear at sites of future bone

2. connective tissue cells differentiate into osteoblasts around blood vessels

3. osteoblasts become osteocytes when completely surrounded by bony matrix

4. connective tissue on the surface forms the periosteum

what are the steps of endochondral ossification?

1. hyaline cartilage model forms at the site of future bone

2. cartilage cells die in lacunae

3. blood vessels come in with osteoblasts which add Ca and P to cartilage

4. osteoblasts become osteocytes when completely surrounded by bony matrix

what is the primary ossification center?

first point that develops into bone

what is the secondary ossification center?

appears in epiphysis last to form endochondral bone

why is a primary and secondary ossification center necessary in endochondral ossification?

to form the growth plate between the diaphysis and epiphysis

what are the four layers of the growth plate?

1. resting zone

2. proliferation zone

3. maturation & hypertrophy

4. calcified matrix