Ch.6 Introduction to the Skeletal System

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skeletal system

The entire framework of bones, their cartilages, along with ligaments and tendons.

Functions of the Skeletal System

1.support- the structural frame work
2. protection- protects sensitive internal organs
3.assistance in movement- allows muscular actions
4. mineral homeostasis-store calcium and other important minerals
5.blood cell production- all blood cells originate in red bone marrow
6.triglyceride storage- as we grow and age some red bone marrow becomes yellow bone marrow

Long Bones

distribute body weight, unevenly distributed, are slightly curved for strength, and absorbs the stress of the body weight.

Short Bones

length is equal, somewhat cube shaped, and nearly equal in length and width.

Flat Bones

are generally thin, provide protection, exstensive surfaces for muscle attachment.

Irregular Bones

complex shapes and cannot be grouped into any other bone category.

Sesamoid Bones

(patella) develope from stress in tendons, changes the angles of pull of a muscle, protects tendons from wear, and always completely ossified

 Regions of a long bone 1. diaphysis

shaft of long bones

2. epiphyses

proximal and distal ends of the bone

2. metaphyses

the regions between the diaphysis and the epiphyses.

epiphyseal plate

a layer of hyaline cartilage that allows the diaphysis of the bone to grow in length

epiphyseal line

when bone growth stops, the cartilage in the epiphyseal plate is replaced by this osseous tissue and results in this bony structure.

 Surface tissues 1.articular cartilage

where the bone forms in articulation (joint) with another bone

 2. Periosteum

a though sheath of dense regular connective tissue that surrounds the bone surface wherever its not covered by articular cartilage

3 Endosteum

thin connective tissue membrane that lines the medullary cavity it contains bone forming cells

medullar cavity

the hollow cylindrical space within the diaphysis that contains yellow bone marrow in adults

calcification

initiated by osteoblast

Osseous Tissue 1 osteogenic cells

unspecified stem cells derived from mescenchyme

2 osteoblast

synthesis / secretes collagen fibers and other organic compounds

3.osteocytes

mature bone cells, are the most numerous cells in osseous tissue and maintain its daily metabolism

4. osteoclasts

huge cells derived from the fusion of as many as 50 moncytes and are concentrated in the the endosteum

 Compact bone

is the more dense of the two, providing much of the strength of long bones.

Perforating or Volkmann's canals

blood ,lymphatic vessels nerves from the periosteum penetrate the the compact bone tissue trough this canal

Central or Haversian canals

vessels in nerves connect with those of the periosteum

Concentric lamellae

this are rings of hard calcified extra cellular matrix

Lacunae

small spaces between the lamellae which contains osteocytes

Canaliculi

tiny and filled with extracelluar fluid

Osteons or Haversian systems

repeated structural units in compact bone tissue

Interstitial lamellae

fragments of older osteons that have been partially destroyed during bone rebuilding or growth

Circumferential lamellae

lamellae that encircle the bone just beneath the periosteum or encircle the medullary cavity

 Spongy bone

has many large spaces. Spongy bone is the predominant tissue in flat bones, and is much stronger than it looks.

trabeculae

lamellae that are arranged in an irregular lattice of thin colums of bone

periosteal arteries

enter the diaphysis through numerous perforating canals and supply blood to the periosteum and outer parts of the compact bone tissue

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