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Skeleton

Bony framework that supports and protects organs and allows movement of the body.

Periosteum

membrane on outside of bone

4 types of CT

1. Cartilage
2.Bone
3.Bone Marrow
4. Periosteum

Functions of Bone

Movement, Protection, Support, Mineral Storage, Hemopoeisis, Energy Storage

Movement

Bone provides leverage for muscle contraction

Protection

Bone protects internal organs from physical injury.

Support

Bone supports soft tissue and provides a point of attachment for skeletal muscles

Hemopoeisis

Blood cell production occurs in RED bone marrow

Energy storage

YELLOW bone marrow contain lipids, an important source of energy.

Axial portion

80 bones that arranged along the longitudinal axis of the body.

Appendicular portion

126 bones appendages

Classification of bones

Long bones, short bones, flat bones, irregular bones, suture bones, sesamoid bones.

Long bones

Longer than they are wide(femur)

Short bones

cube shaped(tarsals)

Flat bones

ribs, sternum, scapula, cranium

Irregular bones

complex shape(vertebrae)

Suture bones

found in cranium(coronal suture)

Sesamoid bones

small bones embedded in tendon (patella)

Proximal Epiphysis

proximal end of a long bone, which is spongy(cancellous) bone arranged in laticework of thin plates

Trabeculae

Laticework of thin plates in end of long bone

Diaphysis

shaft of long bone, which is compact bonce tissue made of concentric rings of hard bone

Distal epiphysis

distal end of a long bone, with the same structure as the proximal epiphysis

Metaphysis

(neck) area where the diaphysis joins the epiphysis

Epiphyseal plate

in growing long bones, a layer of hyaline cartilage that allows the diaphysis to grow in length.

Medullary cavity

where yellow bone marrow is found

Articular cartilage

found where two bones come together(joint). Thin layer of hyaline cartilage that coves the epiphyses. Function is to reduce friction at joint and absorb shock.

Periosteum

thin layer of dense CT membrane around the surface of a bone.

Function of periosteum

repair and nutrition of bone. Also tendons and ligaments attach to it.

Endosteum

membrane that lines the medullary cavity of the bone. It contains osteoprogenitor cells and osteoclasts.

Four types of cells in bone

Osteoprogenitor, Osteoblasts, osteocyte, osteoclast

Osteoprogenitor

Found in inner portion of the periosteum, in the endosteum and canals in bone that contain blood vessels. Function: to undergo mitosis and become osteoblasts.

Osteoblasts

cells that form bone tissue. They secrete collagen and matrix which calcifies to build bone tissue.

Osteocyte

Mature bone cells, the main cells of bone tissue. They maintain bone tissue by exchanging nutrients and wastes with the blood.

Living bone

bone cells and collagen fibers

Non-living bone

Hydroxyapatite

Hydroxyapatite

calcium, phosphorus, and chemical components of the matrix

Elderly

1:3

Bone remodeling

continuous ongoing replacement of old bone tissue with new bone tissue

Remodeling

osteoblasts are constantly forming new bone tissue, and osteoclasts are constantly destroying old bone tissue

Calcium homeostasis

calcium ion level in the blood is strictly regulated, regulated by parathyroid glands and thyroid gland

Parathyroid gland

secrete PTH, increased PTH equals increased blood calcium level

Thyroid gland

secretes the hormone calcitonin, increased calcitonin equals decreased blood calcium level

Repair of bone

1. Fracture Hematoma
2. Fibrocartilaginous callus
3. Bony callus
4.Remodeling

Fracture Hematoma

formation of a blood clot under skin

Fibrocartilaginous callus

organization of the fracture hematoma into granulation tissue called a procallus

Bony callus

Fibrocartilagious(soft) callus becomes bony(hard) callus.

Remodeling

restoration of the bone to near original structure and form

Compact (dense) bone

Consists of osteons with very little space between them
Composes bone tissue of the diaphysis
Function is to protect and support

Haversion canal

dark spot in the middle of compact bone

Spongy bone

1. Done NOT contain osteons
2. Consist of trabeculae surrounding many red-marrow filled spaces.
3. Found in short, flat and irregular bones and in the epiphyses of long bones.
Function is to store RED marrow and provide some support

Ossification

Bone formation

Epiphyseal plate

layer of hyaline cartilage in the metaphysis of growing bone

Structure of the epiphyseal plate

1. Zone of resting cartilage
2. Zone of proliferating cartliage
3. Zone of Hypertrophic cartilage
4. Zone of calcified cartilage

Zone of Resting cartilage

Anchors the epiphyseal plate to the bone of the epiphysis

Zone of Proliferating Cartilage

layer of chondrocytes stacked like coins in columns

Zone of Hypertrophic Cartilage

large chondrocytes, stacked in columns

Zone of Calcified cartilage

only a few cells thick. Calcified matrix, cements epiphyseal plate to the bone of the diaphysis.

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