The Equine Skeleton Flashcards
Define BONE
Bone is a type of connective tissue. Is is the largest part of the skeleton and has a blood supply.
It can be damaged or diseased but can also repair itself, as well as adapt to environmental strength (e.g. training horses on roads improves bone strength).
What is the structure of bone?
The outer layer of bone consists of a dense, ivory covered outer shell called compact bone. This is covered by a further layer called the periosteum. Small holes and channels carry blood vessels from the outer coating to the spongy interior, known as cancellous bone. It is filled with red marrow, which is responsible for the production of red and white blood cells, and yellow marrow, which is mainly fat and can be used as a last resort energy source.
What are the 5 types of bone?
Long, short, sesamoid, flat, irregular
Describe a long bone
They are often limbs e.g. radius, humerus and cannon bones. They are longer than they are wide.
Describe a short bone
They are approximately equal in all dimensions. They can absorb concussion and are therefore found in complex joints that have a lot of movement e.g. the carpus (knee) and tarsus (hock).
Describe a flat bone
They are made up of a flat sandwich of cancellous bones between layers of cortex. They are usually slightly curved, with no cavity for bone marrow. Main function is the protection of vital organs e.g. the skull protects the brain.
Describe an irregular bone
They are unpaired bones on the median plane e.g. vertebrae and hip bones.
Describe a sesamoid bone
They occur along the course of tendons to reduce friction, increase leverage or change direction of pull e.g. the patella (kneecap).
What are the functions of the skeleton?
- protection of organs
- vertebrates depend on levers made of bone attached to muscle that allow locomotion, defence, offence, grasping etc.
- provides storage for minerals such as calcium and phosphorus
What is each section of the equine skeleton called and how many bones in each?
34 bones in the skull 20 bones in each forelimb 20 bones in each hindlimb 37 bones in the ribcage 54 bones in the vetebral column
Define DENSE/CORTICAL (COMPACT) BONE
Compact bone is the hard layer that covers most bones and forms almost the entire shaft of long bones.
Define CANCELLOUS (SPONGY) BONE
Cancellous bone is composed of spicules (small, needle like structures) arranged to form a porous network. The spaces between are usually filled with bone marrow.
Define an OSTEON
An osteon is the basic unit of structure of compact bone, comprising of a Haversian canal and its concentrically arranged lamallae.
Define LAMALLAE
Lamallae is a thin layer, membrane, or plate of tissue, especially in bone. It is arrnaged concentrically within the osteon, around the central Haversian canal.
Define a HAVERSIAN SYSTEM
Haversian systems are formed when several osteons are put together.
Define the MEDULLARY CAVITY
The medullary cavity is the central cavity of bone shafts where red bone marrow/yellow bone barrow is stored.
Define PERIOSTEUM
Periosteum is a dense layer of vascular connective tissue enveloping the bones except at the surfaces of the joints.
Define LACUNAE
Lancunae are small cavities at junctions between lamallae that allow the exchange of nutrients, waste and chemicals.
How does bone growth occur?
There are two ways that bone growth can occur:
1. Adding layers on to the surface (increasing girth).
2. Longitudinal growth from the growth plate (made of cartilage) between the diaphysis and epiphysis.
At sexual maturity the growth plate thickens and fuses.
What are the 3 types of cells in bone?
Osteoclasts - break down old/damaged bone
Osteocytes - carry nutrients and waste products to and from blood vessels
Osteoblasts - repair damaged and build up new bone.
What is endochondral ossification and how does it occur?
It is an essential process during fetal development. #
- Cartilage model develops
- Primary ossification centre develops in the midshafts of long bones
- Secondary ossification centres develop near the end of long bones
- Osteoclasts remove bone while osteoblasts continue to lay it down
- Narrow band of cartilage persists
What are the 4 classifications of joints based on range of movement?
Synarthrosis joint, synchondrosis joint, amphiarthrosis, disthrosis
Describe a synarthrosis joint
These are immovable, fixed joints with bones in very close contact. They are separated by a thin layer of fibrous connective tissue.
Example: the sutures of the skull
Describe a synchondrosis joint
These are connected/bound by hyaline cartilage membrane. Most are temporary but some are permanent. They are almost immovable.
Example: the spinal vertebrae
