Workbook questions session 1 & 2 Flashcards
Can cartilage be converted into bone? Explain. (3marks)
No. Cartilage can be replaced by bone. Cartilage (cartilage matrix) can become calcified thus restricting nutrient and gaseous supply to chondrocytes; chondrocytes thus die. Osseous tissue can be laid on the surface of the calcified matrix, eventually replacing all cartilage by bone.
What factors are responsible for the appearance of tuberosities, tubercles, ridges and grooves on a typical long bone?
Tuberosities, tubercles and ridges – mechanical forces resulting from attachment of muscles, tendons and ligaments to bone.
Grooves – pressures from adjacent structures e.g. nerves and blood vessels
State the mechanical functions of bones?
Provide the rigid framework that supports the body.
Protect vulnerable internal organs (e.g. brain, heart, lungs, etc.).
Make body movements possible by providing anchoring points for muscles and by acting as levers at the joints.
Briefly, what is the function of red bone marrow and erythropoietin? (2 marks)
Production of erythrocytes (erythropoiesis) occurs in red bone marrow.
Erythropoietin is released from the kidney when blood oxygen levels are low (e.g., anaemia) to stimulate red blood cell production
Concerning the functional classification of joints, define the terms; synarthrosis, amphiarthrosis and diarthrosis.
By classification, a joint may be immovable (synarthrosis), slightly movable (amphiarthrosis) or freely movable (diarthrosis).
Joints may also be classified by their structure name the three classification and give examples of each.
Synovial - characterised by ends of bone covered by cartilage & fluidity in cavity e.g. shoulder, knee
Fibrous joints – sutures (tight union between bones of the adult skull) syndesmoses (bones held together by fibrous tissues – interosseous membrane between long bones of the forearm & leg)
Cartilaginous joints – primary cartilaginous (epiphyseal growth plate in long bones) secondary cartilaginous (disc of fibrocartilage in the joint cavity e.g. pubic symphysis, intervertebral joint).
What are the three main components of all synovial joints?
- Articular surfaces cornered by hyaline cartilage, separated by joint cavity
- Synovial membrane (lining cavity) that secretes synovial fluid
- Protective capsule surrounds joints.
What are the factors that restrict movement at synovial joints? (3)
Tension exerted by ligaments of the articular cartilage (e.g. iliofemoral ligament of hip).
Muscle tension (thigh difficult to raise when knee is straight – stretched hamstrings)
Interference by other structures. Stability at joints is also related to the depth of bony articulations.
Which specific tissues of joints are affected in rheumatoid arthritis and osteoarthritis?
RA= Synovium
OA = Cartilage
Concerning the bones of the pectoral girdle and the upper limb, name one bone that develops by intramembranous ossification and one bone that develops by endochondral ossification.
clavicle
humerus, respectively.
What is the basic difference between intramembranous and endochondral
ossification?
Intramembranous – develops directly from mesenchymal tissue
Endochondral – develops by replacing hyaline cartilage model.
What are the three types of bone cells and for each state their function?
Osteoblasts are bone-forming cells (secrete collagen to form a matrix which is calcified)
Osteocytes are former osteoblast cells that become encased in the bone matrix, forming tight junctions with each other across the matrix.
Osteoclasts are bone-breaking cells (resorb bone).
90% of our total body calcium is contained in all bones, and they are therefore a reserve for calcium and other compounds (such as inorganic phosphates). Very generally, why is hypocalcaemia or hypercalcaemia dangerous?
Small decreases of calcium in plasma and extracellular fluid (hypocalcaemia) can cause the nervous system to become more excitable because of increased neuronal membrane permeability with resultant muscular spasm.
Too much calcium (hypercalcaemia) in body fluids depresses the nervous system and causes muscles to become sluggish and weak because the effects of calcium on muscles’ plasma membranes. Bones represent a calcium store for homeostasis.
Write brief notes on the action of parathyroid hormone and calcitonin on bone and state what stimulates their release.
Parathyroid hormone (PTH) and calcitonin (CT) have direct effects on bones. PTH released from the parathyroid glands in response to low calcium levels in the blood stimulates the uptake of calcium from bone, kidneys and the intestinal tract to return calcium levels to normal. PTH increases the number and activity of osteoclasts in bone to increase calcium (and phosphate) resorption from bone and stimulate release of the minerals into blood.
CT is released from specific thyroid cells (parafollicular cells) in response to elevated calcium levels in the blood. CT causes calcium levels to be lowered by inhibiting osteoclastic activity in bone; it also favours calcium uptake by bone, promoting bone formation and decreasing blood calcium levels.
PTH increases blood calcium, while CT lowers it.
(Human growth hormone, thyroid hormones, sex hormones, adrenal cortical hormones and vitamins A,C and D are also important in bone function.
State how nutritional deficiency of the following compounds may affect bone.
i) Calcium / phosphorous Proper nutrition (calcium and phosphorus constitute almost half the content of bone) is essential for normal bone development and maintenance; thus their deficiency causes bones to become brittle.
ii) Vitamin A
Deficiency in vitamin A may cause an imbalance in the ratio of osteoblasts and
osteoclasts, thereby slowing the growth rate.
iii) Vitamin C
Low levels of vitamin C inhibit growth by causing an insufficient production of collagen and bone matrix, a condition that delays the healing of broken bones.
Explain the cause of osteomalacia in the adult and rickets in children.
growth plate is affected and the bones may easily become deformed. Osteomalacia and rickets are defects skeletal resulting from vitamin D deficiency. This leads to widening of the epiphyseal plates, increased number of cartilage cells, wide osteoid seams and decrease in linear growth. Rickets is a childhood disease caused by insufficient mineralisation.
In children with highly pigmented skin and others whose body surfaces are not exposed to sunlight, absorption of ultra-violet rays is markedly affected; ultra-violet rays are involved in vitamin D formation; skeletal deformities such as bowed legs, knock-knees, etc. are common. Osteomalacia leads to demineralisation, an excessive loss of calcium and phosphorus; this condition can be reversed with large doses of vitamin D.
Explain briefly the cause of osteoporosis in post-menopausal women with reference to female reproduction hormones
After menopause, the ovaries produce little oestrogen; low oestrogen affects older bone by destroying it faster than the formation of new bone. Bone mass decreases and it becomes porous and brittle.
