Week 8 Flashcards
Tissue layers of blood vessel
A= endothelium
B= tunica intima: endothelium and internal elastic membrane
C= tunica media: muscle and external elastic membrane
D= tunica adventitia
The descending aorta
Commences at end of aortic arch continues down abdomen
Formally ends by bifurcating into left and right common iliac arteries
Thoracic part- commences at sternal angle of Louis (T4-5), ends at aortic hiatus T12, supplies arterial blood to muscles of chest wall and spinal cord
Abdominal part- commences at T12, ends at L4 bifurcating into left and right common iliac arteries,supracistal plane of pelvis, vertebral level umbilicus, T10 dermatome Renal arteries branch off at L1/L2, has two phases: suprarenal segment and infrarenal segment
Five major arteries arise from abdominal aorta
Coeliac artery: L1
Superior mesenteric artery: L1
Renal arteries: L1/L2
Inferior mesenteric Artery: L3
Left common iliac artery: L4/5
Right common iliac artery: L4/5
Arteries supplying spinal cord, all vertebral levels L1
Arterial tree of lower limb
Common iliac artery: L3/L4, umbilicus, supracristal plane
External iliac artery: L5-S1
-internal iliac artery
Femoral artery : inguinal ligament
-profunda femoris runs through adductor canal
Popliteal artery : adductor canal
Tibial arteries: adductor hiatus
-anterior, posterior : lower border of popliteus
Dorsalis pedis, post tibial artery
Femoral artery
Begins at lower border of inguinal ligament
Passes inguinal ligament at mid point
Ends at apex of femoral triangle
Ends by entering adductor canal
The apex of femoral triangle is an opening in adductor Magnus - adductor canal/ subsartorial canal, hunters canal
Then becomes popliteal artery
Popliteal artery
Starts at the opening adductor canal and ends at adductor hiatus
Then enters diamond shaped anatomical space at back of thigh- Popliteal fossa
In popliteal fossa it gives off a series of geniculate arteries to supply the knee joint
Popliteal artery ends at lower border of popliteus muscle bifurcating into anterior and posterior tibial artery
Anterior tibial artery
Pulses often palpated at its level known as dorsalis pedis
Points of best palpitation are: above the navicular bone, medial to the tendon of extensor hallucis longus
Posterior tibial artery
Larger of the terminal branches of the popliteal artery
Descends deep to soleus then becomes superficial in lower third of the leg
Passes behind the medial malleolus between tendons of flexor digitorum longus and flexor hallucis longus
Below the ankle it divides into medial and lateral plantar arteries which constitute principal blood supply to the foot
Venous tree of the body
Commences at levels of post capillary venules
Ends when venae cava access the right atrium of the heart
Normal drainage venous blood
Longitudinal conduction is that venous blood is conducted from post capillary venules- venules-small veins- larger veins- right atrium
Low pressure system
Has evolved to overcomes an element of the circulatory system where there’s no pump or driving force, tendency of venous blood to pool in lower extremities as a result of gravitational pull
Adaptations venous system
One way valves that prevent back flow of blood to promote venous return to heart
Systemic veins with thin walls enabling them to collapse and obliterate the lumen as the veins collapse they passively pump blood past one valve at a time
Musculovenous pump
Classes of veins
Superficial veins
Deep veins
Perforating veins
Accompanying veins: vaso vasorum, venae commitante(accompany arteries)
Venous blood flows form superficial to deep veins via perforating veins
Sites for venepuncture and saphenous cut down
The great saphenous vein (branch of femoral vein) is accessible through:
A hands breath to the medial edge of patella
In front of medial malleolus
Varicose veins
Perforating veins drain venous blood from superficial to deep veins
If incompetence in valves preventing backflow in perforating veins- venae stasis
Resulting in varicose veins, clotting in stagnant venous blood, raising probability DVT
Nerve supply to lower limb
Lumbar and sacral spinal segments
Lumbar plexus: L1, L2, L3, half L4
Sacral plexus: half L4, L5, S1,S2, S3 S4
The lumbar contribution to sacral plexus is the lumbosacral trunk
The lumbar plexus
Forms behind psoas major
Nerves emerge form medial or lateral border psoas major
Lateral: femoral nerve L2-4, iliohypogastric, ilioinguinal, lateral cutaneous nerve of thigh
Medial: obturator nerve L2-4, lumbosacral trunk half L4, L5
The sacral plexus
Plexus forms in pelvis cavity
Lies in relation to piriformis
Composed of lumbosacral trunk half L4 and L5
Sacral spinal segmental outflow
Supplies nerves to pelvic region, gluteal region, perineal region, lower limb via sciatic nerve
Sensory supply lower limb
Front limb is supplied largely by lumbar segments
Back limbsuppleid mainly sacral segments
Saddle area is sacral segments
Perineal area is sacral segments
Axial lines
Line of junction of two dermatomes supplied from discontinuous spinal levels known as axial line
Limbs have anterior and posterior axial lines
Axial lines mark centre of either pre axial or post axial territories of the limbs
Boundaries between pre axial and post axial compartments are marked out by veins
Sensory nerve territories
Sensory divisions of terminal nerves of lumbar plexus supply skin in territorial domains
Not dermatomes
Visual assessment of the musculoskeletal system
Appearance of skeletal muscles in the body
Symmetry of muscle bulk between left and right sides
Presentation of the limbs and other muscle systems
Posture
Gait etc
Definition of motor unit
Constitutes from the alpha motorneuron and all muscle fibres it supplies
It comprises:
1 alpha-motor neurone
Extrafusal muscle fibres it supplies
Minimal functional unit of the motor system
Definition of a reflex
Involuntary, unlearned, repeatable, automatic reaction to a specific stimulus that doesn’t require brain to be intact
Reflex arc:
A receptor
An afferent fibre
Integration centre
Efferent fibre
Effector organ
Role the muscle stretch reflex play in neurology
Template neural circuit from which all motor circuits are built
Minimal neural circuit that underlies all movements of muscles of body
Neural circuit that sets all motor tone of the body
Muscle Stretch reflex
Stretch activated reflex contraction of skeletal muscle
When a muscle is not contracted it relaxes
A relaxing muscles is effectively lengthening
When muscle length receptors detect stretch they fire action potentials via afferent axons to keep CNS appraised of muscle length at all times
How does muscle stretch reflex work
Action potentials from muscle length receptors are sent to:
The brain via dorsal column
The cerebellum via spino-cerebellar tracts
A copy of that signal is also sent directly to spinal motorneurones
Results in reflex recruitment of motorneurones
Anatomy of stretch reflex
The spinal reflex pathway involves two neurones
A stretch receptor afferent
Efferent neurone
1 synapse in lamina IX of spinal cord
Motor tone
In a normal awake neurological status lower motorneurones tonically supply muscles with background electrical impulses
These lead to background minimal contraction of the muscle
This minimal contraction gives the muscle a small amount of force called muscle tone/motor tone
Motor tone allows us to maintain body posture and hold heads up
Muscle tone in babies
Present but low in-utero
Suppressed in the new born
Returns within months after birth
Return of muscle tone in the new baby informs of the absence or presence of birth injury of the brain
