Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
27 Cards in this Set
- Front
- Back
|
Bone functions
|
Support, protection, movement, storage, blood cell production, energy
|
|
|
Bone functions defined
|
Bone is hard, rigid; cartilage soft but strong
Protection - skull around brain; ribs, sternum, vertebrae Movement - Produced by muscles on bones via tendons Storage - Ca & P stored then released as needed Blood cell production - Bone marrow gives blood Energy storage - yellow marrow contains lipids which stores energy |
|
|
Bone shapes
|
- Long (upper lower limbs
- Short (carpals/tarsals) - Flat (ribs/sternum) - Irregular (vertebrae, sphenoid) |
|
|
Long bone structure
|
Diaphysis - Shaft, compact bone
Epiphysis - End of bone, cancellous Epiphyseal plate - Growth plate, hyaline cartilage until growth stops Epiphyseal line - Stops growing in length Medullary cavity - Red marrow in kids, yellow in adults; rest of skeleton is red Periosteum - Outer = fibrous |
|
|
Periosteum
|
- Inner = single layer bone cells include osteoblasts, clasts, and osteochondral progenitor cells
- Fibers of tendons become continuous w/ fibers of periosteum - Sharpy's fibers - pariosteal fibers penetrate periosteum & into bone. Strengthen attachment of tendon to bone - Endeosteum - more cellular to the similar periosteum -- Lines internal spaces and spaces in cancellous bone & medullary canal - Metaphysis - where diaphysis meets epiphysis |
|
|
Bone facts
|
- Is nearly as strong as cast iron but weighs 1/3 of iron
- Is dynamic - Matrix is 25% water, 25% protein fiber, 50% minerals/salts - Possesses 2 charactoristics rarely found in same materials -- Strong/light weight |
|
|
Components of skeletal system
|
Bone cartilage - Hyaline, fibrocartilage, elastic tendons & ligaments
|
|
|
Bone Histology
|
- Matrix - like reinforced concrete. Rebar is collagen fibers, cement is hydroxyapatite
-- Organic - collagen & proteogylcans -- Inorganic - hydroxyapatite. (CaPO4 crystals) - If mineral removed, bone - too bendable - If collagen removed, bone - too brittle |
|
|
Bone Cells
|
Osteoblasts, Osteocytes, Osteoclasts, Stem Cells (aka Osteochondral Progenitor Cells)
|
|
|
Osteoblasts
|
Osteoblasts - build bone, bone forming cells; process = ossification; cannot divide by mitosis; once osteoblasts are surrounded by matrix, they are called osteocytes
|
|
|
Osteocytes
|
Osteocytes - mature bone cells; can no longer secrete matrix materials; can not divide by mitosis; also called bone-maintaining cells
|
|
|
Osteoclasts
|
Osteoclasts - bone destroyers; function in bone resorption (destruction of matrix); develop from circulating monocytes; contain large number of mitochondria & lysosomes
|
|
|
Osteoblasts (cont'd)
|
Osteoblasts
- Ossification: formation of bone by osteoblasts. Osteoblasts communicatge through gap juntions. Cells surround themselves by matrix |
|
|
Osteocytes (cont'd)
|
Osteocytes
- Mature bone cells surrounded by matrix can make small amounts of matrix to maintain it - Lacunae - spaces occupied by osteocyte cell body - Canaliculi - canals occupied by osteocyte cell processes - Nutrients - diffuse via tiny amount of liquid surrounding cell and filling lacunae & canaliculi. Then can transfer nutrients from one cell to the next via gap junctions |
|
|
Osteoclasts (cont'd)
|
Osteoclasts - resorption of bone
- Ruffled border - where cell membrane borders bone and resorption is taking place - H ions mumped across membrane, acid forms, eats away bone (decalsification) - Release enzymes that digest bone - Derived from monocytes (are formed from stem cells in red bone marrow) - Multinucleated & probably arise from fusion of a number of cells |
|
|
Osteoprogenitor cells / stem cells (cont'd)
|
Osteoprogenitor cells (stem cells)
- Develop from mesenchhyme; can undergo mitosis; also called mesenchyme (osteochondral progenitor cells) become chondroblasts or osteoblasts |
|
|
2 types of bone
|
Compact - Dense
Cancellous - Spongy |
|
|
2 types of bone tissue
|
Woven & Lamellar
|
|
|
Woven bone - collagen fibers randomly oriented
|
- Formed during fetal development and fracture repair
|
|
|
Lamellar bone - Mature bone in sheets called lamellae
|
- Fibers are oriented in one direction in each layer, but in different directions in different layers for strength
|
|
|
Tabeculae
|
Trabeculae - inter connecting rods or plates of bone
|
|
|
Bone development
|
Intramembranous ossification - takes place in connective tissue membrane
Endochondral ossification - takes place in cartilage Both methods of ossification - Produce woven bone that is then remodeled - After remodeling, formation cannot be distinguished as on or the other |
|
|
Intramembranous Ossification
|
- Takes place in connective tissue membrane formed from embryonic mesenchyme
- Begins in 8th week of embryonic development and is complete by age 2 - Forms many skull bones, part of mandible, diaphysis of clavicles - When remodeled, is indestinguishable from endochondral bone - Centers of ossification: locations in membrane where ossification begins - Fontels: large membrane - covered spaces between developing skull bones; unossified - Osteoprogenitor cells differentiate into osteoblasts - A center of ossification forms |
|
|
Intramembranous Ossification (cont'd)
|
- Osteoblasts secrete matrix (salts/collagen)
- Once osteoblasts are completely surrounded by matrix, they no longer secrete matrix material and are called osteocytes - As bone matrix calcifies, trabeculae appear and join to form spongy bone - Some outer layer spongy bone is replaced w/ compact bone - Periosteum forms - Flat bones grow only by appositional growth (growth to outside) - Flat bones can't grow by interior expansion (interstitial growth) as do bones formed by endochondral ossification such as long bones. Interstitial growth results in an increase in length. |
|
|
Endochondral Ossification
|
- Bones of the base of the skull, part of the mandible, epiphyses of the clavicle, and most of the remaining bones of skeletal system
- Cartilage formation begins at end of fourth week of development - Some ossification beginning at week 8; some doesn't begin until age 18-20 - Osteoprogenitor cells differentiate into chondroblasts that produce the cartilage model - Perichondrium forms (outside layer) - Chondrocytes reproduce and continue to secrete matrix; this results in interstitial growth (growth in length) and appositional growth (growth to outside) - Chondrocytes hypertrophy (enlarge) probably due to glycogen accumulation |
|
|
Endochondral Ossification (cont'd)
|
- A pH change occurs which triggers calcification
- Once calcification of area occurs, cartilage cells no longer get nutrients (b/c they can't quickly diffuse into the area - Cartilage cells die - A nutrient artery penetrates the perichondrium and then the bone through a nutrient foramen - This occures in the midregion of the model and osteoprogenitor cells in the perichondrium differentiate into osteoblasts - A periosteal bone collar forms - thin layer of compact bone under the perichondrium - Now the perichondrium is called the periosteum - Capillaries of the periosteum grow into the disintegrading cartilage center |
|
|
Endochondral Ossification (cont'd)
|
- The capillaries produce a primary ossification center, a region where bone tissue will replace cartilage
- In center, osteoblasts bein producing matrix - As the center enlarges, osteoclasts break down the newly formed spongy bone trabeculae, leaving the medullary cavity in the center - The diaphysis, which once was hyaline cartilage, is now replaced w/ compact bone - A secondary ossification center forms, this occurs when blood vessels enter the epiphyses around time of birth - Bone formation of the epiphyses is similar to bone formation of the diaphysis EXCEPT… -- Spongy bone remains in the center of the epiphyses -- No medullary cavity forms -- Hyaline cartilage remains as articular cartilage on the outside of the epiphyses -- Until bone growth is complete, there will be an epiphyseal plate between the epiphyses and diaphysis □ This plate allows the bone to grow longer |
