Skeletal System Flashcards
How many bones are in the human body?
206
List the functions of the skeleton
- Support framework for the body
- Forms boundaries (i.e, the skull)
- Attachment for muscles and tendons
- Permits movement (joints)
- Haematopoeisis (production of blood cells in the red bone marrow)
- Mineral homeostasis (mostly calcium & phosphate)
- Triglyceride storage (in yellow bone marrow)
The skeleton accounts for what % of body weight?
18%
What is bone marrow?
A tissue throughout the central cavity of bones, through which we produce all of our blood cells after birth.
This is where we house lots of stem cells, that can specialise as RBC’s, WBC’s or platelets.
99% of the calcium in your body is found where?
In the bones / skeletal system
Where are triglycerides (fats) stored?
In the yellow bone marrow
Why is yellow bone marrow called ‘yellow’?
Because the fat stored within it makes it look yellow.
What are osteogenic cells?
Bone stem cells.
They later specialise to become osteoblasts or osteoclasts.
What are osteoblasts?
Cells that build bone. Immature/juvenile cells.
Which bone cells secrete collagen, ground substance and other components of bony matrix
Osteoblasts
How do osteoblasts become osteocytes?
When they get trapped within their own bony secretions and become stationery and fully mature.
What are osteocytes and what is their function?
Osteocytes are mature bone cells. They maintain the daily metabolism of bone, such as nutrient exchange.
List the 4 types of bone cells.
- Osteogenic cells
- Osteoblasts
- Osteocytes
- Osteoclasts
Which are the biggest bone cells?
Osteoclasts
Osteoclasts are huge cells, derived from the fusion of what?
As many as 50 monocytes (specialised WBC’s)
How do osteoclasts dissolve the surface of bone (resorption)?
By releasing lysosomal enzymes and acids directly onto the bone surface.
What is the difference in function between osteoblasts and osteoclasts?
Osteoblasts build bone matrix, osteoclasts dissolve bone matrix.
Why do osteoclasts have a ‘ruffled border’ on the side of their cell membrane that faces the bone surface?
To increase surface area for enzyme release and reactions, increasing their efficiency at breaking down bone.
What is ‘resorption’?
The breakdown of bone matrix
Which bone cells work together to ‘remodel’ bone throughout life?
Osteoblasts and osteoclasts
What 2 types of bone is the skeleton formed from?
Compact and spongy bone
What % of our skeleton is made of compact bone?
80%
Describe compact bone
Compact bone is found beneath the periosteum, on the outside of bones. It makes up the bulk of the diaphysis of long bones. It contains few spaces and is strong.
What is an osteon?
A small structural sub-unit of compact bone. Osteons look like slices of tree trunks. They are aligned in the same line as stress.
How many parts does an osteon have?
An osteon has 4 parts
List the 4 parts of an osteon
- Haversian canal
- Lamellae
- Canaliculi
- Lacunae
Within an osteon (small, structural, sub-unit of compact bone) what is housed within the Haversian Canal?
Blood vessels and nerves
What are lamellae?
Concentric rings of calcified extracellular matrix, containing minerals and collagen.
Lamellae are found within osteons.
What are canaliculi and where are they found?
Canaliculi are found within osteons. They are a mini system of interconnected canals that provide a route for nutrients and waste within bones.
Why does bone need a rich blood supply?
Because the skeleton is a living structure. Bone is connective tissue and it is alive.
What part of an osteon ensures that we have a blood supply to the bone?
The Haversian canal. It houses blood vessels and nerves.
Why do our bones have nerves running through them?
So that we can feel sensation in them and avoid activity that can break them.
Which part of an osteon gives strength to compact bones?
The lamellae.
They are concentric rings of calcified extracellular matrix, containing minerals and collagen.
Where are osteocytes located within the osteons of compact bone?
Osteocytes are located within the lacunae of osteons, which are essentially small spaces.
Which type of bone does not contain osteons?
Spongy bone doesn’t contain osteons
Describe spongy bone.
Spongy bone is made up of an irregular lattice of thin columns called trabeculae, which are arranged along lines of stress.
Where would you find trabeculae?
In spongy bone
Where would you find spongy bone?
Spongy bone makes up the interior of short, flat and irregular bones, and the ends of long bones.
Spongy bone is always covered with compact bone.
What is spongy bone always covered with?
Compact bone
Why are osteons in compact bone, and trabeculae in spongy bone always arranged along lines of stress?
To ensure that when we’re being active, we are distributing forces in the most efficient and effective way possible, so that our bones can act as shock absorbers.
What is the most abundant mineral in bone?
Calcium phosphate
There is also magnesium, sulphate and potassium
What is the extracellular matrix in bone predominantly made of?
Collagen fibres and minerals.
Collagen is the scaffolding. The minerals contribute to the hardness of the bone.
Define ‘long bones’.
Bones that are longer in length than they are in width.
Define ‘diaphysis’.
The shaft of a long bone
Define ‘epiphysis’.
The end of a long bone
Give 3 examples of long bones
Femur, tibia, humerus
Why are many long bones slightly curved?
To allow them to better distribute forces. If our bones were completely straight, they wouldn’t have any ability at all to bow under compression.
Where would you find the epiphyses?
At the proximal and distal ends of long bones.
Which structure separates the diaphysis from the epiphysis in long bones?
The epiphyseal growth plate
What is the epiphyseal growth plate?
A layer of hyaline cartilage that separates the diaphysis from the epiphysis in long bones, and allows the diaphysis to grow in length.
How long are epiphyseal growth plates active for?
Until the age of 18 - 21
They then fuse and become bone (which is why we typically stop growing at this age)
Name 2 long bones that contain some red bone marrow.
Humerus, Femur
What is the periosteum?
The outer layer of bone is covered by the periosteum, with the exception of areas that are covered in cartilage (ie, the ball and socket epiphyseal contacts)
What is the central cavity in the diaphysis of long bones called?
The medullary cavity
What does the medullary cavity in long bones contain?
Red / yellow bone marrow
All bone marrow starts off as red bone marrow. True or false?
True
Following a body trauma, yellow bone marrow can be converted to red bone marrow, to produce more blood cells. True or false?
True