Lesson 18 Skeletons

bone

aka osseous tissue

hard, dense connective tissue that forms most of the adult skeleton, the support structure of the body

cartilage

a semi-rigid form of connective tissue

provides flexibility and smooth surfaces for movement

functions of skeletal system

• supports the body

• facilitates movement

• protects internal organs

• produces blood cells

• stores and releases minerals and fat

yellow marrow

contains adipose tissue

• the triglycerides stored in the adipocytes of the tissue can serve as a source of energy

red marrow

site of hematopoiesis (BC production)

• RBC, WBC, platelets

diaphysis

tubular shaft that runs between the proximal and distal ends of the bone

• walls made of compact bone

medullary cavity

hollow region in the diaphysis filled with yellow marrow

epiphysis

wider section of the bone with spongy bone

• each epiphysis meets the diaphysis at the metaphysis

metaphysis

narrow area of the bone that contains the epiphyseal plate (growth plate)

• epiphyseal plate becomes the epiphyseal line when cartilage is repalced by osseous tissue

endosteum

membranous lining of the medullary cavity, where bone growth, repair, and remodeling occur

periosteum

outer surface of the bone covered with a fibrous membrane

• contains blood vessels, nerves, and lymphatic vessels that nourish compact bone

• tendons and ligaments attach to bones at the periosteum

• covers entire outer surface, except where bones form joints

what covers the epiphyses at the site of joints

articular cartilage, a thin layer of cartilage that reduces friction and acts as a shock absorber

hydroxyapatite

calcium phosphate and calcium carbonate combine, then incorporate other inorganic salts like magnesium hydroxide, fluoride, and sulfate as it crystallizes

• give bones their hardness and strength

• collagen provides flexibility

types of cells in bone tissue

osteoblasts

osteocytes

osteogenic cells

osteoclasts

osteoblast

form new bone; found in the periosteum and endosteum

• do not divide; synthesize and secrete the collagen matrix and calcium salts

osteocyte

the primary cell of mature bone and the most common type of bone cell

• located in the lacuna and is surrounded by bone tissue

• lack mitotic activity

• communicate and receive nutrients via processes extending from the canaliculi

osteogenic cell

undifferentiated with high mitotic activity; only bone cells that divide

• found in the periosteum and marrow

• differentiate and develop into osteoblasts

• differentiate and develop into osteoblasts

osteoclast

responsible for bone reabsorption and breakdown

• found on bone surfaces, are multinucleated, and originate from monocytes and macrophages

compact bone

denser, stronger bone tissue

• found under the periosteum and in the diaphyses of long bones, where it provides support and protection

spongy (cancellous) bone

contains osteocytes housed in lacunae

• algined in a trabculae (lattice-like network of matrix spikes)

• forms along lines of stress to provide strength

nutrient foramen

small openings in the diaphysis that provide nourishment to bones