Skeletal System Flashcards
List the five functions of the skeletal system.
Support
Protection
Movement
Mineral storage
Blood cell formation
What does the skeletal system provide along will support?
Structure and shape
Give three examples of bones with a protection function.
Cranium
Thoracic cage
Long bones
How does the skeletal system have a role in movement?
Bones are used for leverage
In relation to its storage function and calcium, what is the skeletal system often called?
A calcium reservoir
What minerals are stored in bones?
Calcium and lipid
Where is lipid stored in bones?
In the yellow marrow of the medullary cavity
How much calcium is stored in bones?
1 kg of calcium
What is blood cell formation often called?
Haematopoiesis
What type of blood cells are made by bones?
Red and white blood cells
Where are red blood cells made?
Red bone marrow
Where are white blood cells made?
Red marrow
Where do red blood cells mature?
In the red marrow
What are the three components of connective tissue (definition)?
Cells and fibres in a matrix (also called ground substance)
Are bones a type of connective tissue?
Yes
What does ‘osteo’ refer to?
Bone
Name the three type of bone cells.
Osteoblasts
Osteocytes
Osteoclasts
What is the precursor cell for bone cells?
Osteoprogenitor cell
What is an osteoprogenitor cell?
A type of stem cell that can form osteoblasts
What is the role of the osteoblasts?
They secrete the ‘framework; (the ground substance in its raw form) for calcium phosphate deposition (matrix)
What is the matrix for bone?
Calcium phosphate
Explain ossification.
Osteoblasts secrete matrix around themselves which then becomes ossified/calcified
What is another word for ossified?
Calcified
What is the name given to osteoblasts because of their function?
Bone builders - as they form bone
What are osteocytes?
Mature osteoblasts - osteoblasts which have become trapped in their own matrix
What is the lacunae?
The space in the matrix where osteocytes are trapped
What is the space in the matrix where osteocytes are trapped called?
Lacunae
What is the precursor cell for osteoclasts?
Monocyte
What is the role of the osteoclast?
Matrix degradation - bone degradation
What is matrix degradation?
Demineralisation and reabsorption of the matrix
Why does the matrix need to sometimes be degraded?
To allow stored calcium to be released and enter the blood stream - occurs when bone is broken down
What determines the rate of bone turnover?
The ‘tug of war’ fight between the osteoblasts and osteoclasts
What stimulates bone turnover?
It is stimulated when there is stress on a part of the body - reaction to outside mechanical stimuli
How do lacunae appear under a microscope?
They appear as little black dots amongst matrix
What are lamellae?
These are layers of matrix forming osteons
How do lamellae appear under a microscope?
They appear as rings which radiate and get bigger
What are osteons?
Lots of lamellae together with a blood vessel in the centre
How do blood vessels in the centre of an osteon appear under the microscope?
They appear as a hole in the osteon
Why do bones repair so quickly?
They are extremely vascular - each osteon has its own blood supply
What are canaliculi?
Channels between lacunae
What is the role of canaliculi?
2
They allow osteoblasts in lacunae to transport materials between each other
They dump waste into the central canal
How do osteoblasts use canaliculi?
Cytoplasmic extensions of osteocytes penetrate canaliculi
How do canaliculi appear under the microscope?
They appear as black lines spread out from lacunae
How many types of bone tissue are there?
2
What are the different types of bone tissue?
2
Compact/cortical bone
Spongy/Trabecular/Cancellous bone
What is another name for compact bone?
Cortical bone
What are two other names for spongy bone?
Trabecular
Cancellous
Describe compact bone.
Heavy
No gaps
Describe spongey bone
Light but strong
Has gaps - allows bone marrow to be stored
Name the parts of long bone.
Epiphysis
Diaphysis
Metaphysis
What is the epiphysis?
2
Spongy bone found at each end of long bone
Contains red bone marrow
What is the diaphysis?
3
Middle of long bone
Compact bone
The inside is the medullary canal
What is the metaphysis?
Where the epiphysis meets the diaphysis
What is the metaphysis also called?
Epiphyseal plates
What is found in the medullary canal?
Red and yellow marrow
What is the periosteum?
The outside covering on bone
What is the endosteum?
The wall of the medullary cavity
What is the outside covering on bone called?
The periosteum
What is the endosteum?
The wall of the medullary cavity
What is another name for ossification?
Osteogenesis
How many stages are there to osteogenesis?
Embryo
Infants
Adults
Describe osteogenesis in an embryo.
Its the formation of the skeleton
Describe osteogenesis in infants.
Its growth and development of the skeleton
Describe osteogenesis in adults,
This is bone repair and remodeling
How often is the entire skeleton replaced?
It is replaced every 10 years
How many types of osteogenesis take place in embryos?
Two
What are the two types of osteogenesis that take place in embryos?
Intramembranous
Endochondral
Give two examples of intramembranous embryonic osteogenesis.
Skull
Clavicles
What bones are grown through endochondral embryonic osteogenesis?
Everything except the skull and clavicles
Explain intramembranous growth.
Mesenchymal stem cells secrete matrix and eventually become osteoblasts
What are mesenchymal stem cells?
Stem cells - cell that can become several types of cells but in bone they form osteoblasts
Explain endochondral growth.
3
This starts as cartilage framework
The cartilage is replaced by bone tissue - calcification
Replaces existing bone and cartilage
In general what are the two types of bone growth?
Epiphyseal growth (length)
Oppositional growth (circumferential)
Explain epiphyseal growth.
7
Osteoblasts invade epiphyseal area and replace cartilage with osseous tissue
Cartilage at epiphyses is replaced
Bone increases in length
Chondrocytes ‘run away’ from osteocytes which are ‘chasing’ them which forces bones to become longer
This process is largely controlled by hormones
Osteoblasts catch up with chondrocytes
Plate then becomes calcified and no further changed in bone length can occur
What are chondrocytes?
Cartilage producing cells
What is the name of cartilage producing cells?
Chondrocytes
Why do we stop growing in our late teens?
This occurs when the osteoblasts manage to catch up with the chondrocytes and calcify the cartilage at epiphyses
Explain oppositional growth.
3
Osteoblast activity beneath periosteum (osteons develop) – osteoblasts secrete matrix – bone becomes thicker
Osteoclast activity resorb inside creating marrow cavity – nibble away at endosteum and reabsorbing it back into system
Bone gets fatter and fatter – osteoblast and osteoclast activity slows down in late teens due to changes in hormones
What controls bone growth?
Hormones
What are the two skeletons in the body?
The axial and appendicular skeleton
What is the appendicular skeleton?
All bones except the spine and skull
Limbs and pelvis etc
What is the axial skeleton?
the skull and spine
Classify bones.
6
Short Long Flat Sutural Irregular Sesamoid
What are short bones?
Give 2 examples.
Small carpal bones
Bones in wrist
7 bones in the tarsus (ankle)
What are long bones?
Give 3 examples.
Metacarpals in hands
Phalanges
Radius and ulna
What are flat bones?
Give 2 examples.
Parietal bone of skull
Ilium of pelvis
What are sutural bones?
Give an example.
Joining two bones together
Sutures in skull are the only example
What are irregular bones?
Give an example.
Vertebra
What are sesamoid bones?
Give an example.
Osseous tissue embedded in a ligament and tendon
The patella
What is the healthy range for calcium homeostasis?
Ca++ 2.2 - 2.6 mmol.L-1
Describe the range of calcium levels in the body.
2
They are never stagnant - they always move up and down between two set points
There is a very small window for change
What is the name for low calcium levels?
Hypocalcaemia
What is the name for high calcium levels?
Hypercalcaemia
Describe hypercalcaemia,
2
Reduced excitation of nerve and muscle tissue
Hyper polarises excitation tissue - nervous and muscle tissue - it is harder to excite them and depolarise them - to do their thing
What are the symptoms of hypercalcaemia?
4
Insomnia
Depression
Polyuria
Death
What is polyuria?
Excessive urination to excrete excess calcium through the urinary system
Describe hypocalcaemia.
2
Overexcitation of nerve and muscle tissue
It is much easier to excite the excitable tissues - much less stimulus is needed for these tissues to become depolarised
What are the symptoms of hypocalcaemia?
3
It leads to convulsions
Throws your heart out of rhythm - arrythmia
Death
How many hormones are involved in Ca++ homeostasis?
Two
What are the two hormones involved in calcium homeostasis?
Calcitonin
Parathyroid hormone
Where is calcitonin produced?
The thyroid cell by C cells
Where is parathyroid hormone produced?
By chief cells in the parathyroid gland
What is the role of calcitriol?
It converts vitamin D to calcium in the kidney
What is the method of homeostasis used in maintaining Ca++ levels?
Negative feedback - opposing effects of calcitonin and parathyroid hormone
