The Musculoskeletal System Flashcards
What are the functions of the musculoskeletal system?
- support
- protection of vital organs
- movement (limbs, chewing, breathing)
- production of red blood cells in bone marrow
-calcium reserve
How does the musculoskeletal system support the body?
Maintaining body shape and suspending organs.
What type of tissue is bone?
Solid connective tissue.
Name the two types of bone.
Cortical and cancellous bone.
Describe cortical bone.
Compact/woven bone. Solid bone forming the outside of bone.
Describe cancellous bone.
Spongy bone. A meshwork of bone that forms the inside.
What are osteocytes, osteoblasts, and osteoclasts?
Cells within the bone.
What is an osteocyte?
A cell.
What is an osteoblast?
An active cell (builder).
What is an osteoclast?
Destroyer (resorb old bone).
When are osteoclasts most active?
During growth.
How do osteoblasts work?
When blood calcium levels are high, they create new bone to store excess calcium.
How do osteoclasts work?
When blood calcium levels are low, they break down areas of bone to release calcium into the blood circulation.
What role do bone cells take in the event of a fracture?
Osteoclasts will destroy damaged bone and osteoblasts will produce new bone.
What are the types of bone?
- long bones
- short bones
- flat
- sesamoid
- irregular
What are sesamoid bones?
Small pebble-shaped bones that form in tendons.
Explain parts of a long bone.
- Diaphysis – main shaft
- Epiphysis – prominences forming
the ends - Physis - also called the growth
plate - Metaphysis – area adjacent to the
physis - Medullary cavity – central cavity
filled with bone marrow
Name two types of bone development.
- intramembranous ossification
- endochondral ossification
Where does intramembranous ossification occur?
In flat bones.
Explain intramembranous ossification.
The outline of the bone is formed by membranes, bony tissue forms
between the membranes
A – The outline of the bone is formed by
membranes with stem cell inside
B – Stem cells become osteoblasts and
start producing bone matrix
C – Eventually, the entire area becomes
bone and the trapped osteoblasts become
osteocytes
Where does endochondral ossification occur?
All other bones that aren’t flat bones.
Explain endochondral ossification.
The outline of the bone is formed by cartilage, which is then gradually
replaced by bone from the inside out.
A – A cartilage model of the skeleton forms
B – Osteoblasts in the centre start to turn this model into bone
C – Secondary areas in the epiphyses also start to become bone
D – Gradually the entire model is replaced by bone except for the articular cartilage
covering the epiphyses and the physis (growth plate). The physeal cartilage will
continue to lengthen the bone until the animal is fully grown, at which point, the
physis ‘closes’ and also becomes bone.
What are the four stages to bone healing?
- Haematoma formation
* Haemorrhage at the trauma site leads to the formation of a
haematoma - Soft Callus
* The fracture is fused together by fibrous tissue - Hard Callus
* The fibrous tissue eventually becomes bone and forms a solid union - Remodelling
* Over time, the hard callus is re-formed to produce a ‘normal’ bone
What is bone tissue mostly composed of?
Calcium phosphate (CaPO4)
What is needed in a diet to maintain a healthy skeleton? Where can these be found?
Calcium and phosphorus. Milk, eggs, and a bone meal.
What is the ideal calcium : phosphorus ratio?
Between 1.1:1 and 1.3:1
Which vitamin is needed for calcium and phosphorus absorption in the digestive tract?
Vitamin D.
What can low levels of calcium, phosphorus, and Vitamin D lead to?
= reduced bone formation
* Rickets - Poor and abnormal growth in puppies
* Osteomalacia in adults = softened, brittle bone
* Slow or incomplete fracture healing
What type of tissue is cartilage and what is it composed of?
Solid connective tissue. Proteins and a few cells (chondrocytes).
What can high levels of calcium, phosphorus, and Vitamin D lead to?
- Increased bone formation often causing tissue mineralisation.
This can lead to kidney and digestive failure, and calcium
deposits in the skin and muscle. - High blood calcium can also affect the heart
What are the three types of cartilage?
- Hyaline cartilage – found covering the articular surfaces (the ends of bones
within joints) - Elastic cartilage – found in the pinna and larynx
- Fibrocartilage – found in cartilaginous joints
What is the difference between tendons and ligaments?
Ligaments - A band or ring of connective tissue, attaching two bones together
Tendons - A narrow band of connective tissue linking a muscle to a bone
What is aponeurosis?
A wide sheet of connective tissue attaching a muscle to either a bone
or another muscle.
What is the periosteum?
The connective tissue layer surrounding a bone, adhered tightly to it
surface
What is bone marrow and where is it found?
Haemopoietic tissue found inside the medullary cavity of long bones.
How does bone marrow differ in neonates?
In the neonate, red bone marrow fills the whole medullary cavity. Over time this is
gradually replaced by fatty tissue, called yellow marrow. In the adult, bone marrow is
only present in the ends of long bones.
Name the three types of joints.
Fibrous, cartilaginous, and synovial.
Explain fibrous joints.
These can also be called fused joints.
They are immovable. Bones meet and
are joined together with fibrous tissue.
Over time this becomes bone and the
bones are fused together.
Example – bones of the skull
Explain cartilaginous joints.
Two bones are joined together by
fibrocartilage. There are two types.
Cartilaginous joints with no movement
Solid fibrocartilage forms between the
two bones and forms a stable union.
Example – mandibular symphysis
Cartilaginous joints with small
amount of movement
Fibrocartilage joins the two bones
and in the centre is a gelatinous pulp
that allows some movement.
Example – Inter-vertebral discs
Explain synovial joints.
Movable joints.
What are the ends of the bones in a synovial joint covered with and why?
Hyaline cartilage for smooth movement.
What is a synovial capsule filled with and why?
Synovial fluid for lubrication.
Where are intra-capsular ligaments found?
inside the synovial capsule.
Where are extra-capsular ligaments found?
Outside or within the wall of the synovial capsule.
Define menisci.
These are fibrocartilaginous pads that provide shock absorption and protection.
What are the types of synovial joints?
Plane joints – flat bone surfaces that have a gliding motion. One bone slides in a
parallel direction over the other bone.
Hinge – allows movement in one direction, i.e. bending and straightening
Condylar – curves surfaces fit together, allows movement in two planes.
Ball and Socket – sphere of bone (the ball) fits into a depression (the socket) in other
bone, allows movement in all 3 planes
Pivot – a peg of bone fits into a ring or semi-circle of bone, allows rotation
What are the three types of muscle?
Skeletal, smooth, and cardiac.
What else can skeletal muscle be known as and why?
Striated muscle because it appears stripy under a microscope
Describe skeletal muscle.
Skeletal muscle cells (also called fibres) are very long and are bundled
together and bound by connective tissue to form a muscle.
Skeletal muscle is attached to the skeleton. It is voluntary muscle (consciously
controlled). It creates limb and trunk movement, including walking, chewing and
breathing.
Describe smooth muscle.
Smooth muscle cells are very small. Smooth muscle is involuntary (unconsciously
controlled). Smooth muscle is found forming layers within organs.
Examples – small intestine, bladder, blood vessels, iris of the eye, pilo-erector muscles.
Describe cardiac muscle.
Cardiac muscle is only found in the heart. Cardiac muscle is also involuntary. It has
its own internal pacemaker but can be controlled by unconscious
parts of the brain and some hormones.
Explain muscle contraction.
Skeletal muscle cells are filled with layers of overlapping proteins called myofibrils.
When the muscle is stimulated to contract, these layers slide over one another and
shorten the muscle.
What are antagonists?
Muscles often work in pairs or groups to provide opposite actions. These are called
antagonists.
What movements can muscles produce?
- Flexion - bending of a limb joint (decrease the angle)
- Extension - straightening of a limb joint (increase the angle)
- Protraction - moves the limb cranially
- Retraction - moves the limb caudally
- Abduction - moves the limb laterally
- Adduction - moves the limb medially
Keep in mind – a muscle is only active when it is contracting. The movement a
muscle makes is only when the muscle is contracting, i.e. shortening in length.
