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Chapter 6: The Skeletal System

Parts of chapter 6 that focuses on: Structure of Bone, Bone Formation, and Division of the Skeletal System
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Function of Skeletal System: Support
Provides a structural framework for the body by supporting soft tissues and providing points of attachment for the for the tendons of most skeletal muscles
Function of Skeletal System: Protection
Protection of many internal organs from injury
Function of Skeletal System: Assistance in Movement
Work with muscles to produce movement
Function of Skeletal System: Mineral Homeostasis
Release of minerals into blood to maintain critical mineral homeostasis
Function of Skeletal System: Blood Cell Production
Produces blood cells
Red Bone Marrow
Within certain bones, a connective tissue that consists of developing blood cells, adipocytes, fibroblasts, and macrophages; present in develpoing bones of the fetus and in some adult bones, and ends of the arm bones and thigh bones
Hemopoiesis
produces red blood cells, white blood cells, and platelets
Function of Skeletal System: Triglyceride Storage
Store triglycerides
Yellow Bone Marrow
Consists of mainly adipose cells and also contains a few blood cells; changes from red to yellow bone marrow with age
Long Bones
Greater in length than width; usually somewhat curved for strength; Include: thigh(femur), leg(tibia and fibula), arm(humerus), forearm(ulna and radius), and fingers and toes(phalanges)
Short Bones
Almost cube shaped; nearly equal in in length and width; Include: most wrist and ankle bones
Flat Bones
thin; affords significant protection and provides extensive surfaces for muscle attachment; Includes: cranial bones, sternum(breastbone), ribs, and scapulae(shoulder blades)
Irregular Bones
have complex shapes; cannot be grouped into any specific category; Includes: vertebrae and some facial bones
Diaphysis
the bone's body: the long cylindrical, main portion of the bone
Epiphyses
the distal and proximal ends of the bone
Megaphyses
regions where the diaphysis joins the epiphyses
Epiphyseal plate (growth plate)
layer of hyaline cartilage that allows the diaphysis of the bone to grow in length; found only in growing bones
Epiphyseal Line
When bone growth in length stops, the cartilage in the epiphyseal plate is replaced by bone and resulting in a bony structure
Articular Cartilage
a thin layer of hayline cartilage covers part of the epiphysis where the bone forms a joint with another bone; reduces friction and absorbs shock at freely moveable joints
Periosteum
a tough sheath of dence irregular connective tissue that surronds the bone surface wherever it is not covered by articular cartilage; contains bone forming cells that allow bone to grow in diameter or thickness but not in length; Function: protects the bone, assists in fracture repair, helps nourish bone tissue, and acts as an attachment point for ligaments and tendons
Medullary Cavity (Marrow Cavity)
a hollow, cylindrical space within the diaphysis that contains fatty yellow bone marrow in adults
Endosteum
membrane that lines the medullary cavity
Osseous Tissue (Bone)
the major structural and supportive connective tissue of the body; forms the rigid part of the bone organs that make up the skeletal system.
Calcification
initiated by osteoblasts
Tensile Strength
resistance to being stretched of torn apart
Osteogenic Cell
unspecialized stem cells derived from mesenchyme; only bone cells to undergo cell division; found among the inner portion of the periosteum, in the endosteum, and in the canals within bone that contain blood vessels
Mesenchyme
tissue from which almost all connective tissues are formed
Osteoblasts
Bone building cells; synthesize and secrete collagen fibers and other organic components needed to build the extracellular matrix of bone tissue; surrond themselves in extracellular matrix, becoming trapped in their secretions, forming osteocytes
Blasts
secrete extracellular matrix
Osteocytes
formed form osteoblasts; mature bone cells; the main cells in bone tissue
Cytes
maintain the tissue
Osteoclasts
huge cells derived from the fusion if as many as 50 monocytes and are concentraded in the endosteum; release powerful lysosomal enzymes and acids that digest the protein and mineral components of the bone extracellular maxrix
Resorption
Part of the normal development, growth, maintenance, and repair of bone
Clasts
break down extracellular matrix
Compact Bone Tissue
bone tissue that contains few spaces between osteons; forms the external portion of all bones and the bulk of the diaphysis of long bones
Osteons (Haversian Systems)
basic unit of structure in adult compact bone, consisting of a central canal
Haversian (Central) Canal
a channel that contains blood vessels, nerves, and lymphatic vessels
Concentric Lamellae
rings of hard, calcified extracellular matrix that resembles the growth rings of a tree
Lacunae
Small spaces between the lamellae that contain ostercytes
Canaliculi
extending from all directions from the lacunae, small tiny channels filled with extracellular fluid; connect lacunae with one another and with central canals
Perforating (Volkman's) Canals
connect with those of the medullary cavity, periosteum, and haversian canals
Compact Bone
Strongest type of bone tissue; provides protection and support and resists the stresses produced by weight and movement
Spongy Bone Tissue
does not contain osteons; consists of units called trabeculae; makes up most of the bone tissue of short, flat and irregularly shaped bones
Trabeculae
an irregular latticework of thin columns of bone
Ossification
process by witch bone forms
Intramembranous Ossification
bone forms directly within mesenchyme arranged in sheetelike layers that resemble membranes;the simpler method of bone formation
Ossification Center
cite where bone develops; mesenchymal cells cluster together and differentiate into osteogenic cells then into osteoblasts
Endochondiral Ossification
bone forms within hayline cartilage that develops from mesenchyme; the more complex method of bone formation; the replacement of cartilage by bone
Cartilage model
formed from chrondroblasts that secrete cartilage extracellular matrix
Perisoteum
a tough fiberous connecitve tissue membrane that covers the outside of the diaphysis; anchored firmly to the outside of the bone on all surfaces except articular cartilage.
Primary Ossification Center
a region where bone tissue will replace most of the cartilage
Secondary Ossification Center
develop around the time of birth; bone formation is similar to that in primary ossification centers except that spongy bone remains in the interior of the epiphyses; proceeds outward from the center of the epiphysis toward the outer surface of the bone
Articular Cartilage
hyaline cartilage that covers the epiphyses
Epiphyseal (growth) Plate
responsible for the lengthwise growth of long bones
Bone Remodeling
the ongoing replacement of old bone tissue by new bone tissue; also removes injured bone, replacing it with new bone tissue; may be triggered by factors like exercise, and changes in diet
Bone Resorption
the removal of minerals and collagen fibers from bone by osteoclasts
Bone Deposition
the addition of minerals and collagen fibers to bone by osteoblasts
Spurs
thick bumps that form if too much mineral material is deposited in the bone; interfere with movement at joints
Fracture
any break in a bone
Partial Fracture
an incomplete break across the bone, like a crack
Complete Fracture
a complete break across the bone; the bone is broken into two or more pieces
Closed (Simple) Fracture
fractured bone does not break through the skin
Open (Compound) Fracture
he broken ends of the bone protrude through the skin
Parathyroid Hormone (PTH)
most important hormone that regulates Ca²⁺ exchange between bone and blood, secreted by the parathyroid glands
Calcitonin (CT)
another hormone involved in calcium homeostasis
Demineralization
Loss of bone minerals
Axial Skeleton
Consists of 80 bones; consists of the bones that lie around the longitudinal axis of the human body
Axis
an imaginary line that runs through the body's center of gravity from the head to the space between the feet
Appendicular Skeleton
consists of 126 bones; contains the bones of the upper and lower limbs plus the bone groups called girdles
Girdles
connect the limbs to the axial skeleton