The Skeletal System Flashcards
what are the five functions of the vertebrate skeletal system?
1) support the body
2) provide framework for movement
3) protect vital organs
4) store calcium
5) synthesize the formed elements of the blood (cells), which occurs in flat bone marrow
hematopoiesis
formation of formed elements of the blood, occurs in the marrow of flat bones
the vertebrate endoskeleton can be divided into:
axial (skull, vertebral column, rib cage) and appendicular components
connective tissue
consists of cells and the materials they secrete, ex. bones
fibroblast
single progenitor from which all connective tissue cells are derived
what are some fibroblast derived cells?
bone, collagen (strong fibrous protein), elastin (fibrous extracellular protein which gives tissue the ability to stretch and regain its shape), adipocytes (fat cells), chondrocytes (cartilage cells), osteocytes (bone cells)
how is connective tissue different from other tissue types in the body?
connective tissue is primarily extracellular material witha few cells scattered in it
matrix
the extracellular material which consists of fibrous proteins and ground substance (thick, viscous material composed of proteoglycans which are surrounded by a large amount of water and give tissues thickness and firmness)
what are the two types of connective tissue?
loose connective tissue and dense connective tissue
loose connective tissue
basically packing tissues; include areolar tissue (the soft material located between most cells through the body) and adipose tissue (fat)
dense connective tissue
tissues that contain large amounts of fibers (e.g. tendons, ligaments, cartilage, bones)
what are the two primary bone shapes?
flat and long
flat bones
ex. scapula, ribs, bones of the skull, the location of hematopoiesis, important for organ protection, shell of compact bone surrounding inner spongy bone with red marrow-site of hematopoiesis)
long bones
bones of the limbs, important for support and movement
diaphysis
the main shaft of a long bone (tube of compact bone containing yellow marrow)
epiphysis
the flared end of a long bone, shell of compact bone surrounding core of spongy bone)
what are the structures of bone?
compact (hard and dense) or spongy (porous, always surrounded by a layer of compact bone)
bone marrow
non-bony material found in the shafts of long bones and in the pores of spongy bones
red marrow
found in spongy bones within flat bones, the site of hematopoiesis which increases in response to erythropoietin
yellow marrow
found in the shafts of long bones, is filled with fat and is inactive
what are the two principal ingredients of bones?
collagen and hydroxyapatite
hydroxyapatite
a solid material consisting of calcium phosphate crystals
what is the structure of spongy bone?
disorganized structure in which many spikes of bone (spicules/trabeculae) surround marrow-containing cavities
what is the structure of compact bone?
specific organization
osteon/Haversian system
the basic unit of compact bone structure
central/Haversian canal
a hole in the center of the osteon which contains blood, lymph vessels, and nerves
lamellae
concentric rings of bone surround the central Haversian canal
canaliculi
tiny channels that branch out from the central Haversian canal to spaces called lacunae
lacunae
spaces that contain an osteocyte
osteocyte
mature bone cell, have long processes that extend down the canaliculi to contact other osteocytes through gap junctions
perforating/Volkmann’s canals
channels that run perpendicular to central canals to connect osteons
cartilage
strong but very flexible extracellular tissue secreted by chondrocyte cells
what are the 3 types of cartilage?
hyaline, elastic fibrous
hyaline cartilage
strong and somewhat flexible (ex. larynx and trachea, joins lined by articular cartilage/hyaline cartilage)
elastic cartilage
found in structures such as the outer ear, epiglottis, that require support and more flexibility than hyaline cartilage, contains elastin
fibrous cartilage
very rigid and is found in places where very strong support is needed (ex. pubic symphysis and the intervertebral disks of the spinal column)
is cartilage innervated?
no, it is also avascular (does not contain blood vessels), receives nutrition from surrounding fluid
ligaments
connect bonds to other bones, dense connective tissue
tendons
connect bones to muscles, dense connective tissue
joint
the point where one bone meets another
synarthroses
immovable joints, basically points where two bones are fused together
amphiarthroses
slightly movable joints, provide both movability and a great deal of support (ex. vertebral joints)
diarthroses
freely movable joints, ex. ball and socket, hinge
all movable joints are supported by:
ligaments
movable joints are lubricated by:
synovial fluid which is kept within the joint by the synovial capsule
endochondral ossification
how most bone growth occurs: hyaline cartilage is produced and then replaced by bone
intramembranous ossification
the synthesis of bone from an embryonic tissue called mesenchyme (results in flat bones)
process of long bone growth:
epiphyseal plate seen between diaphysis and epiphysis, chondrocyte division forces epiphysis and diaphysis apart, cartilage is replaced by bone/ossified which is stimulated by growth hormone, rate of ossification is slightly faster than the rate of chondrocyte cell division, when diaphysis and epiphyses meet and fuse together, lengthening can no longer occur, fusion point/epiphyseal line is seen
epiphyseal plate
a disk of hyaline cartilage that is actively produced by chondrocytes
remodeling
process by which bones are continually degraded and remade
osteoblasts
the cells which make bone by laying down collagen and hydroxyapatite, synthesizes bone until the osteoblast itself is surrounded by bone and only a lacuna is left (at which point it becomes an osteocyte)
osteocyte
mature osteoblast, after it has completed synthesis of bone
osteoclasts
continually destroy bone by dissolving the hydroxyapatite crystals
what replaces bone destroyed by osteoclasts?
osteoblasts
liberation of calcium and phosphate into the bloodstream is a result of:
an increased ratio of osteoclast (break down) to osteoblast (synthesis) activity
parathyroid hormone
stimulates osteoclast activity in the bones, increases reabsorption of calcium in kidneys and stimulates conversion of vitamin D into calcitriol, indirectly increases intestinal calcium absorption (via calcitriol)
calcitriol
may stimulate minor osteoclast activity in bones, increases reabsorption of phosphorus in kidneys, increases intestinal absorption of calcium
calcitonin
inhibits osteoclast activity in bones and decreases reabsorption of calcium in kidneys
