Week 1 - Bones Flashcards
What are the diff. tissues working together in the bone
Osseous tissue
Cartilage
Dense connective tissue
Epithelium
Adipose tissue
Nervous tissue
What % of human body weight is bone? And what % of the body’s calcium does it store?
18%
99%
What does red bone marrow consist of?
Developing blood cells
Adipocytes
Fibroblasts
Macrophages w/in a network of reticular fibres.
Where can red bone marrow be found
Developing bones of the foetus + in adult bones:
- Pelvic bones
- Ribs
- Sternum
- Vertebrae
- Skull
- Ends of bones of humerus
- Femur
Bone marrow for newborns
All red + involved in hemopoeisis
What’s in the extracellular matrix?
15% H20
30% collagen fibres
55% crystallised mineral salts
Whats the most abundant crystallised mineral salt in the body?
Calcium phosphate
What does calcium phosphate do in the bones?
Combines w. calcium hydroxide —-> Crystal of hydroxyapatite.
As these form they combine w. other mineral salts i.e calcium carbonate.
Then crystallise when deposited in the framework formed by collagen fibres of the extracellular matrix == Calcification
What is calcification initiated by?
Osteoblasts
External functions of the skeletal system
Protection of internal organs
Movement facilitation
Supports the body
Internal functions of the skeletal system
Prod. of blood cells
Storage of minerals
Storage of TG
Where are TG stored in the skeleton?
Yellow bone marrow
What are the 4 main aspects of a long bone
Epiphysis
Diaphysis
Periosteum membrane
Endosteum membrane
Define the epiphysis
Ends of bones
Joint surface is covered w. articular cartilage
What separates the diaphysis from the epiphysis
Epiphyseal line
At around what ages do long bones stop growing in LENGTH?
18-25
What happens after long bones stop growing in length?
Epiphyseal cartilage disappears
Epiphyseal plate closes
Becomes visible on x-rays as an epiphyseal line
Define metaphyses
Regions between diaphysis + epiphysis
What does a metaphysic contain on a growing bone?
An epiphyseal/growth plate
Hyaline cartilage that allows the diaphysis fo the bone to grow in length
Define the diaphysis
Long, tubular shaft of the bone.
A collar of compact bone surrounds a central medullary/marrow cavity.
Define the medullary cavity
In the diaphysis.
Filled w. yellow bone marrow + in adults contains fat.
Interior of all bones consists largely of spongy bone.
Where is the periosteum
Covers the outer bone surface
What does the periosteum consist of
Dense irregular connective tissue
Osteoblasts
Nerve fibre blood - secured by sharpers fibres
Lymph vessels - secured by sharpeys fibres
Where is the endosteum
Covers the internal bone surfaces
Define the articular cartilage
Thin layer of hyaline cartilage
Covers epiphysis where bone forms an articulation w, another bone = joint.
What is the function of articular cartilage
⬇️ friction + absorbs shock at freely moveable joints.
Why is the repair of damaged articular cartilage limited?
Due to lack of perichondrium + bv.
What are the 2 main types of bones?
Cortical (compact/hard)
Trabecular (cancellous/spongy/soft)
Cortical (compact/hard) bone
Low porosity (5-10%)
Strong + dense (80% of skeleton)
Epiphysis (thin shell)
Diaphysis (shaft, thicker)
Trabecular (cancellous/spongy/soft)
High porosity (30-90%)
Lighter + less dense than cortical
20% of skeleton
Remaining space is filled w. marrow + fat
List the main components of the microscopic structure of compact bone
Osteon
Osteoblasts + clasts
Osteocytes
Osteoid
Osteoprogenitor cells
COMPACT BONE
Osteon
Repeating structural units of compact bone tissue.
COMPACT BONE
Osteoblasts
Make + deposit components of bone extracellular matrix.
Where are osteoclasts often found?
In the endosteum lining the marrow cavity.
What do osteoclasts do
Degrade + resorb bone for remodelling.
Secrete protein-digesting enzymes.
Dissolve bone matrix + release stored minerals (osteolysis).
Define osteocytes
“watcher cells”
Sit in bone + monitor its current status.
Mature bone cells that maintain protein + mineral content of bone matrix.
Also help repair damaged bone.
Where can osteocytes be found
Between lamellae of matrix
What is the osteoid?
Unmineralized bone matrix
What are osteoprogenitor cells?
Mesenchyme stem cells that divide to prod. osteoblasts.
Only bone cells that undergo cell division.
Define concentric lamellae
Circular plates of mineralised extracellular matrix of increasing diameter, surrounding a small network of bv + nerves located in the central canal.
What are lacunae?
Small spaces between the conc. lamellae that contain osteocytes
Canaliculi
Radiate from the lacunae in all directions.
Filled w. extracellular fluid.
What can be found in the canaliculi
Slender fingerlike processes of osteocytes