SAQs Flashcards
(11 cards)
List two common complications of the surgical treatment of hip fracture
- Deep vein thrombosis / pulmonary embolism
- Surgical site infection
Due to immobility and surgical stress, especially in the elderly or immunocompromised patients.
Define T and Z scores as reported on bone density results
T-score: Compares the patient’s bone mineral density to the young adult mean (age 20-30)
* T greater than -1 is normal
* T between -1 and -2.5 is osteopenia
* T less than -2.5 is osteoporosis
Z-score: Compares the patient’s bone mineral density to matched population (age, sex, ethnicity)
* Useful for assessing secondary causes of osteoporosis
* Especially in premenopausal women and men under 50
T-scores are used to diagnose osteopenia and osteoporosis.
Briefly describe the origin, structure and function of osteoblasts
- Origin - mesenchymal stem cells
- Structure - mononuclear, cuboidal cells, found on bone surfaces
- Function - synthesize bone matrix (type 1 collagen), promote mineralization
Osteoblasts are crucial for bone formation.
Briefly describe the origin, structure and function of osteoclasts
- Origin - haematopoietic stem cells
- Structure - large multinucleated cells with ruffled border
- Function - resorb bone by secreting acid and enzymes, cathepsin K
Osteoclasts are essential for bone resorption.
List three endocrine modulators of normal bone metabolism and state their principal mechanisms of action
- PTH: Increases serum calcium, stimulates osteoclast activity, promotes renal calcium reabsorption, activates vitamin D
- Calcitriol (Vitamin D): Increases intestinal absorption of calcium and phosphate, facilitates bone mineralization
- Oestrogen: Inhibits osteoclast mediated bone resorption, promotes osteoblast survival and function
PTH’s chronic elevation stimulates RANKL expression on osteoblasts, activating osteoclasts indirectly.
List two common causes of falls in the elderly
- Postural hypotension
- Poor balance or muscle weakness
Causes include medications, autonomic dysfunction, sarcopenia, or neurological impairment.
Name the three functional divisions of the cerebellum and for each state its principal function
- Vestibulocerebellum: Balance and eye movements, input from vestibular system
- Spinocerebellum: Co-ordination of trunk and limb movements, posture, input from spinal cord
- Cerebrocerebellum: Planning and initiation of voluntary movements, input from cerebral cortex
Each division has a specific role in motor control.
Describe the golgi tendon reflex
- Protective reflex that prevents excessive tension in muscles
- When tension increases, golgi tendon organs are activated
- Afferent signals travel via 1B sensory fibres to the spinal cord
- Inhibits alpha motor neuron of the contracting muscle and activates the antagonistic muscle
- Result - muscle relaxation, prevents tendon or muscle damage
This reflex helps maintain muscle integrity during contraction.
Describe the structure of the semi-circular canals
- Three canals: anterior, posterior, and horizontal
- Arranged orthogonally to detect head rotation in all planes
- Each canal contains endolymph and expands at one end into an ampulla
- The ampulla houses the crista ampullaris
- Contains hair cells embedded in a gelatinous structure called the cupula
- Part of the membranous labyrinth within the bony labyrinth
The structure is crucial for balance and spatial orientation.
Explain what happens within the semi-circular canals when a person’s head rotates
- Head rotation causes endolymph within the canals to lag behind due to inertia
- This fluid movement deflects the cupula, bending the stereocilia of the hair cells
- Depending on the direction:
- Deflection towards kinocilium = depolarization and increased firing rate
- Deflection away from kinocilium = hyperpolarization and decreased firing rate
- The brain interprets these signals as angular acceleration
This mechanism is vital for detecting changes in head position.
Name two vestibular disorders
- Benign paroxysmal positional vertigo
- Meniere’s disease
BPPV is caused by dislodged otoliths, while Meniere’s disease is characterized by excess endolymph.
