Skeleton Flashcards
(55 cards)
Functions of the skeletal system
- Supports framework for the body
- Forms boundaries
- Attachment to muscles & tendons
- Permits movement (joints)
- Haematopoiesis from red bone marrow
- Mineral homeostasis (mostly calcium & phosphate)
- triglyceride storage (yellow bone marrow)
What are osteogenic cells
Bone stem cells - only bone cell to undergo division which produces osteoblasts
What are osteoblasts
Bone-building cells
They synthesise & secrete collagen & other components of bony matrix
When they are trapped they become osteocytes
What are osteocytes
Mature bone cells
Maintain daily metabolism of bone, such as nutrient exhange
What are osteoclasts
Huge cells derived from the fusion of as many as 50 monocytes (WBCs)
Cell membrane is a ruffled border which releases powerful lysosomal enzymes & acids which digest bone matrix
Resorption = breakdown of bone matrix
What is compact bone
80% of skeletal bones
Contains few spaces & is strong
Found beneath the periosteum of all bones & makes up the bulk of the diaphysis of long bones
Peri = layer surrounding Diaphysis = shaft
What is an osteon & its four parts
Osteon = structural unit of compact bone
- Haversian canal
- Lamellae
- Canaliculi
- Lacunae
What is spongy bone
No osteons, Instead consists of an irregular lattice of thin columns called trabeculae that are arranged along lines of stress
Spaces between trabeculae help make bone lighter & can be filled with bone marrow & blood vessels
It is always covered with compact bone
Makes up the interior of short, flat & irregular shaped bones & end of long bones
What main minerals are found in the bone matrix
The most abundant is calcium phosphate. This combines with other mineral salts such as magnesium, sulphate, potassium
These minerals are deposited & crystallise (harden) in the framework formed by collagen fibres of the matrix. Together these minerals contribute to the hardness of bone
What is the haversian canal
The canal within osteons that contains blood vessels & nerves
What is lamellae
Concentric rings of calcified extracellular matrix containing minerals & collagen within osteons
What is canaliculi
Mini system of interconnected canals that provide a route for nutrients/waste within osteons
What is lacunae
Small spaces with osteocytes found within osteons
What is the epiphyseal plate
A layer of hyaline cartilage that separates the epiphyses & the diaphysis of long bones that allows the diaphysis to grow in length
How does the periosteum assist bone growth & repair
It is aouble-layered membrane with a tough outer ‘fibrous layer’ & an inner ‘osteogenic layer’ that contains osteoblasts & osteoclasts that assist in bone growth & repair
What are the two ossification pathways used to produce bone
- Intramembranous: bone develops from connective tissue sheets & all flat bones (ie skull) & the clavicles develop this way
- Endochondral: bone develops by replacing hyaline cartilage
What hormones promote osteoblast activity
Growth hormone Thyroid hormone Oestrogen Testosterone Calcitonin
What hormones promote osteoclast activity
Parathyroid hormone
Cortisol (& steroid medications)
What is the mineral calcium’s affects on bone homeostasis
Blood calcium levels have to be tightly controlled to ensure proper blood clotting, nerve & muscle function
Calcium exhange is regulated by the parathyroid glands & the thyroid gland
What are the parathyroid glands affects on blood calcium
Increases overall blood calcium
Increase activity of osteoclasts (resorption)
Stimulate kidneys to reabsorb & retain calcium in blood
Increases formation of calcitrol
What is calcitonin & its affects on bone calcium
A hormone that lowers blood calcium levels
It is secreted by para-follicular cells of the thyroid gland
It inhibits osteoclasts & promotes osteoblast deposition of calcium in the bones
Overall results in increased bone formation & decreased blood calcium
What is vitamin D’s affects on bone calcium
It facilitates calcium absorption jn the intestines & is directly involved in bone turnover
Vitamin D3 works closely with K2
D3 assists absorption of calcium jntk the blood whilst K2 activates a protein ‘osteocalcin’ which controls utilisation of calcium in the body (depositing it in bones)
What affects the body’s vitamin D levels
Decrease with increase in age
Combination of factors such as:
Low sun exposure
Reduced dietary absorption
Reduced ability to produce an active form of vitamin D
High alcohol intake reduced vitamin D conversion into its active form
Magnesium deficiency - it is a co-factor needed for conversion of vitamin D
What effects do exercise have on bones
Within limits, bone can become stronger in response to mechanical stress (weight-bearing exercise & gravity pull)
Leads to increased mineral deposition & increased collagen production
