Structure and Function of the MSK System – The Skeleton Flashcards
What is the primary cell of the connective tissue and what are their purpose
Fibroblasts
Produces and maintains ECM of connective tissue
What can the matrix of the connective tissue be divided into
Ground substance and protein fibres
Functions of the bone
Provides the bodies framework – support and protection
Acts as a calcium store for the body
Groups of bone
Long bones – consist of a shaft and two ends (tibia)
Short bones – nearly equal in length and diameter (carpal)
Flat bones – thin and plate-like (skull)
Irregular bones – shape that does not fit in above categories
Examples of Irregular bone
Complex shape – vertebrae
Bone contains air spaces – ethmoid bone
What is the composition of the bone matrix
Three main components:
Organic matrix (osteoid – 25%)
Inorganic mineral content (50%)
Water (25%)
Two types of bones and how are they caused
Collagen fibre arrangement leads to two types of bone – woven (immature) and lamellar (mature)
What is the organic matrix (osteoid) composed off
Osteoid composed of 90% collagen fibres (primarily type I) and 10% non-collagenous proteins (glycoproteins, osteocalcin) – forms the framework of bones
What dies the cortical bone contain
Constitutes the shaft (external layer) of bones
Consists of osteons – composed of haversian canal that is concentrically surrounded by lamellae
What are osteons
– cylindrical structures containing a mineral matrix & osteocytes, connected by canaliculi
Osteons are aligned in the same direction along lines of stress and help resist bending/fracture
What are Harversian canal
– contains bone’s blood vessels and nerve fibres
What is the trabecular bone made up of
Constitutes the inner layer of bones
Consists of trabeculae – arrangement of rods and plates
Trabeculae arranged so that one side of bone bears tension and the other withstands compression
What are the characteristics of woven bones
Disorganised fibre organisation
Osteoblasts produce osteoid rapidly
In all fetal bones – later replaced by lamellar bone
Present following fractures – woven bone is initially laid down as healing occurs
What are the characteristics of lamellar bone
Created by remodelling of woven bone
Collagen fibres are highly organised and aligned in sheets
Collagen fibres run in opposite directions to provide tensile strength
Contains less osteocytes than woven bone
What are osteoblasts and what are their function
Bone building cells
Synthesise and secrete the organic parts of bone ECM (osteoid)
Initiate and control the mineralisation of osteoid via hydroxyapatite
Produce many products including enzymes (alkaline phosphatase), growth factors, hormones (osteocalcin), and collagen
Structure of ostoblasts
OBs are cuboidal in shape and become flattened when surrounded by the matrix
What are the fucntions of osteoclasts
Bone breaking (resorption) cells Critical in the maintenance, repair and, remodelling of bones Produce enzymes (acid phosphatase) that dissolve the organic and inorganic components of bone
Strcuture of osteoclasts
Large, multinucleated cells formed by the fusion of many cells derived from monocytes circulating in the blood
Contain many small projections (microvilli) that extend into the bone’s surface
What are osteocytes
Derived from osteoblasts
Most abundant cell type in mature bone
Found within fully formed bone
Occupy a small gap known as a lacuna
Signal other osteocytes in response to bone deformations in bone remodelling process
What specialised cell does the cartilage composed of
The chondrocyte
Charactersitics of cartilage
Composed of collagen, proteoglycans (aggrecan), glycosaminoglycans (GAGs), and water
Contains one highly specialised cell type – the chondrocyte
Avascular – obtains all nutrients through diffusion
Three types – hyaline, elastic, fibro
What are the purpose of chondrocytes
Occupy small cavities in the cartilage known as lacunae
Produce and maintain the cartilaginous matrix
Absorb nutrients via diffusion from the perichondrium
What is chondrogenesis
Process of cartilage formation from mesenchymal cell condensation
These then differentiate into chondroblasts and begin secreting molecules to form ECM
Where are hyaline cartilage found
Found on joint surfaces of long bones (articular cartilage), trachea, larynx, end of ribs (costal cartilage)
