Introduction to Anatomy of the Limbs Flashcards
What are the functions of the bones?
To support body shape To act as levers for muscle action To protect internal organs To form red blood cells To store minerals
What properties do bones have?
Cable-like flexibility and resistance to tension, because framework is collagen.
Pillar-like stiffness and resistance to compression conferred by impregnation of collagen with crystalline mineral (hydroxyapatite).
How are long bones grossly structured?
2 epiphysis regions at either end with a long diaphysis in between.
How is lamellar bone arranged?
Outer hard layer of compact lamellar bone (cortical bone).
Inner layer of interlacing struts of lamellar bone: cancellous bone (spongy/ trabecular).
Makes the bone lighter and medullary cavity needed for bone marrow.
What is the difference between trabecular and woven bone?
Trabecular bone, although irregularly shaped, is lamellar.
What is the periosteum?
The outer layer of bones, with fibrous and cellular layers. Roles in bone growth and repair, vascular and good sensory nerve supply.
Describe intramembranous ossification.
Mesenchymal cells produce the matrix, called osteoid. Osteoid is mineralised with calcium salt deposits. Mesenchymal cells differentiate into osteoblasts to form an ossification centre. As ossification proceeds, some osteoblasts are trapped in bony pockets (lacunae) and transform into osteocytes. Blood vessels grow into the area to maintain the metabolism of the bone. The initial bone formed is cancellous, but this can be subsequently remodelled into compact bone. Periosteum forms around the bone and traps a surface layer of osteoblasts.
Describe endochondral ossification.
Within existing foetal cartilage models. Cartilage calcifies: chondrocytes die. Periosteal osteoclasts cut channels for vessels. Osteoblasts enter to build bone.
Long bones, which must support large forces while growing. Shaft ossifies first, followed by epiphyses. Growth continues by ossification at growing cartilage plate between them. Epiphyseal plates remain unossified for years.
Give properties of growth of bone.
Can grow without compromising its support functions (via epiphyseal plates).
Increases or decreases bulk and density in response to use.
Bone has large blood supply (nutrients and O2). Osteocytes maintain matrix but can activate osteoblasts for new bone building.
Can alter its external and internal shape in response to pattern of use - remodelling.
What is apposition?
The addition at the exterior of periosteum. Osteoblasts and osteoclasts create ridges and grooves on bone surface. Blood vessels align in grooves. Osteoblasts build new osteons around vessels.
Explain how bleeding helps in fracture healing.
The haematoma becomes infiltrated by fibrous matrix and invaded by cartilage/ bone progenitors.
Woven bone –> endochondral ossification.
Which bones comprise the axial and appendicular skeletons?
Axial = skull, spine, ribs and sternum. Appendicular = everything else.
Why are the positions of flexors and extensors in the upper and lower limb flipped around?
Since the lower limb undergoes permanent pronation resulting in a twisting of the dermatome fields in foetal development.
The result: flexors are anterior in the upper limb but posterior in the lower limb.
What is a compartment of a limb?
An area with distinct function with the same blood and nerve supply.
Which spinal nerves supply the upper and lower limbs?
Brachial plexus (C5-T1) supplies upper limbs, Lumbosacral plexus (L2-S3) supplies lower limbs.
