Chapter 6: Bones and Skeletal Tissue (A)

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Skeletal Cartilage

made of variety of cartilage tissue, which consists primarily of water. Contains no blood vessels and is surrounded by a layer of dense irregular connective tissue, perichondrium. Contains all 3 types of cartilage: Hyaline, Elastic, and Fibrocartilage

Resilience

ability to spring back to original shape after being compressed

Perichondrium

(around the cartilage) acts like a girdle to resist outward expansion when the cartilage is compressed. Contains blood vessels from which nutrients diffuse through matrix to reach the cartilage cells

Hyaline Cartilage

provide support with flexibility and resilience. Are the most abundant of skeletal cartilages.

Include: (1) articular cartilages: cover ends of most bones at movable joints, (2) costal cartilages: connect ribs to sternum (breastbone), (3) respiratory cartilages: form skeleton of larynx (voicebox), (4) nasal cartilages: support external nose

Elastic Cartilages

contain more stretchy elastic fibers, able to stand up to repeated bending. Found in external ear and the epiglottis (flap that bends to cover the opening of the larynx each time we swallow)

Fibrocartilages

highly compressible and have great tensile strength, consist of chondrocytes and thick collagen fibers. In sites with heavy pressure and strength, such as padlike cartilages of knee and discs between vertebrae

Appositional Growth

(1st type of cartilage growth) cartilage forming cells in surrounding perichondrium secrete new matrix against the external face of the existing cartilage tissue.

Interstitial Growth

(2nd type of cartilage growth) lacunae-bound chondrocytes divide and secrete new matrix, expanding the cartilage from within.

Axial Skeleton

form long axis of body and includes bones of the skull, vertebral column, and rib cage. In general these bones are involved in protecting, supporting, or carrying other body parts.

Appendicular Skeleton

consists of bones of the upper and lower limbs and girdles (shoulder bones and hip bones) that attach the limbs to the axial skeleton.

Classification of Bones

1. Long Bones
2. Short Bones
3. Flat Bones
4. Irregular Bones

Long Bones

longer then they are wide, has a shaft plus 2 ends [All limb bones except the patella (kneecap) and the wrist and ankle bones are long bones]

Short Bones

roughly cube-shaped (bones of wrsit and ankle are examples)

Sesamoid Bone

(shaped like a sesame seed) are special type of short bones that form in tendons . Vary in sizes and numbers in individuals. Some alter directions of pull of tendon other their functions are unknown

Flat Bones

thin, flattened and usually a bit curved (sternum, scapulae, ribs, and most skull bones are flat bones)

Irregular Bones

complicated shapes that fit none of the preceding classes (include vertebrae and hip bones)

Functions of Bones

1. Support (for body and soft organs), 2. Protection (for brain, spinal cord and vital organs, 3. Movement (levers for muscle action), 4. Storage (minerals [calcium and phosphorus] and growth factors), 5. Blood Cell Formation (occurs in marrow cavities of certain bones), 6. Triglyceride (Fat) Storage (fat is stored in bone cavities and represents a source of stored energy for the body)

Bone Markings

bones display projections, depressions, and openings that serve as sites of muscle, ligament, and tendon attachment, as joint surfaces, or as conduits for blood vessels

Projections

are bulges that grow outward from the bone surface include head, trochanters, spines, and others.

Depression

cavities that indent the bone, usually serve to allow passage of nerves and blood vessels

Openings

usually serve to allow passage of nerves and blood vessles

Compact Bone

smooth and solid outer layer of every bone

Spongy Bone

internal to compact bone, a honeycomb of small needle-like or flat pieces called trabeculae

Diaphysis

shaft of bone, forms long axis of bone, constructed of thick compact bone that surrounds meduallar cavity (contains fat/ yellow marrow)

Epiphyses

the bone ends, exterior is made of compact bone and their interior contains spongy bone. Joint surface of each epiphysis is covered with thin layer of articular (hyaline) cartilage [cushions opposing bone ends during joint movement and absorbs stress]

Epiphyseal Line/Plate

between diaphysis and epiphysis of an adult bone. A disc of hyaline cartilage that grows during childhood to lengthen bone. sometimes called metaphysis

Perisoteum

white glistening, double layered external surface of the entire bone except the joint surface. Has out fibrous layer (dense irregular connective tissue) and an inner osteogenic layer (consists of osteoblasts)

Osteoblasts

secrete bone matrix elements, and osteoclasts

Osteoclasts

bone destroying cells

Osteogenic Cells

primitive stem cells that give rise to the osteoblasts

Nutrient Foramina

nerve fibers, lymphatic vessels, and blood vessels from periosteum enter the diaphysis from this opening

Perforating (Sharpey's) Fibers

tufts of collagen fibers that extend from its fibrous layer into bone matrix, which secure periosteum to underlying bone

Endosteum

delicate connective tissue membrane that covers internal bone surfaces

Diploe

another name for spogny bone is flat bones

Red Marrow

(Hematopoitec Tissue) typically found within the trabecular cavities of spongy bone of long bones and in the diploe of flat bones

Red Marrow Cavities

trabecular cavities of spongy bone of long bones and diploe of flat bones

Osteon/ Haversian System

the structural unit of compact bone that is riddled with passageways that serve as conduits for nerves, blood vessels, and lymphatic vessels. Each osteon is an elongated cylinder oriented parallel to long axis of bone

Lamella

column like matrix tube of an osteon (compact bone often times called lamellar bone)

Central Canal/ Haversian Canal

runs through the core of each osteon and contain small blood vessels and nerve fibers that serve need of the osteons cells

Perforating Canals/ Volkmann's Canal

second type of canals, lie at right angles to the long axis of the bone and connect the blood and nerve supply of periosteum to those in the central canals and medullary cavity

Lacunae

occupied by spider-shaped osteocytes at junctions of the lamelle

Canaliculi

hairlike canals that connect lacunae to each other and to the central canal

Osteocytes

maintain the bone matrix, also act as stress or strain sensors in cases of bone deformation.

Interstitial Lamellae

incomplete lamellae that lie between intact osteons, either fill gaps between forming osteons or are remnants of osteons that have been cut through by bone remodeling

Circumferential Lamellae

located deep to periosteum and superficial to endosteum and extend around entire circumference of the diaphysis and resist twisting of long bone

Trabeculae

in spongy bone, align along lines of stress, no osteons, Contain irregularly arranged lamellae, osteocytes, and canaliculi, Capillaries in endosteum supply nutrients

Chemical Composition of Bone

organic and inorganic components; matrix, proper combination allows bones to be durable and strong without being brittle

Organic Components

include cells (osteogenic, osteoblasts, osteocytes, and osteoclasts) and osteoid (organic part of the matrix)

Osteoid

makes up 1/3 of matrix, includes ground substances (composed of proteoglycans and glycoprotiens) and collagen (provide tensile strength and flexibility) fibers, secreted by osteoblasts

Hydroxyapatites

mineral salts, 65% of bone by mass, Mainly calcium phosphate crystals, Responsible for hardness and resistance to compression

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