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The Structural Basis of Medical Practice (SBMP) - Human Gross Anatomy, Radiology, and Embryology
Answer Guide for Lower Limb and Thorax Essay Examination (36 pts) - September 05, 2003
The College of Medicine at The Pennsylvania State University
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[ Heart Valves and Coronary Flow ] [ Flexion and Extension of the Toes ]
[ Femoral Triangle ]
Note. The following is a guide to answering the questions and is not the "answer."
Discuss the structure and function (including blood flow to the coronary vessels) of the semilunar valves and the atrioventricular valves (12 pts)
- The valves of the heart direct blood flow in one direction
- Between the atria and the ventricles are the atrioventricular valves
- Between the ventricles and arterial trunks are the semilunar valves
- Healthy valves permit little to no back flow
- Integrated with the skeleton of the heart
- Located in the ventricles (atrioventricular valves) and at the base of the arterial trunks (semilunar valves)
- The atrioventricular valves and the semilunar valves are closed by the pressure (they are not closed by muscular contraction applied to the cusps)
- IVC to rt atria to tricuspid to rt ventricle to pulmonary valve to pulmonary artery to lungs to pulmonary veins to left atria to biscupid (mitral) valve to left ventricle to aortic valve to systemic circulation to coronary arteries during diastole
- Atrioventricular valves close (lub) during systole whereas the semilunar valves close (dub) during diastole
- Atrioventricular valve - Tricuspid
- Between the right atria and the right ventricle
- Three cusps open into the right ventricle
- Three papillary muscles (extensions of trabeculae carne) - anterior, posterior, and septal
- Cusps are stabilized by chorda tendeneae - fibrous cords between cusps and papillary muscles
- Ventricular contraction raises pressure - blood pools on ventricular side of cusps causing the cusps to approximate each other and close the valve
- Adjustments by the papillary muscles and chorda tendeneae provide support and prevent eversion of the cusps into the atria
- Note - contraction of the papillary muscles, in the absence of ventricular contraction, open, not close, the atrioventricular valves
- Atrioventricular valve - Biscuspid (Mitral Valve)
- Between the left atria and the left ventricle
- Two cusps open into the left ventricle
- Two papillary muscles - anterior and posterior
- Resists extreme pressure generated by left ventricular contraction
- Semilunar valve - aortic valve
- Located at the base of the aortic trunk
- Prevents reverse flow from the aorta to the left ventricle during diastole
- Negative pressure of left ventricle and elastic recoil of systemic arteries move aortic blood toward the valve
- Opened by blood flow during systole - cusps move toward aortic wall and block coronary ostia
- Three cusps - no papillary muscles or chorda tendeneae
- Left and right coronary cusps and a non-coronary cusp
- Nodule - weighted fibrous thicking at the midline of the free edge of each cusp aids in approximating the cusps and closing the valve
- Aortic sinus - space between the wall of the aorta and each cusp
- Valve closed by pressure - blood pools in the aortic sinuses during diastole and aproximates the nodules
- Semilunar valve - pulmonary valve
- Located at base of pulmonary trunk
- Prevents reverse flow from the pulmonary trunk to the right ventricle during diastole
- Operation is the same as aortic valve except that there are not coronary cusps (no ostia in pulmonary trunk)
- Blood flow to the coronary vessels
- Coronary arteries are perfused during diastole when heart muscle is relaxed
- During systole the coronary ostia are blocked by the open cusps of the aortic valve
- During diastole blood pools in the aortic sinuses and closes the aortic valve.
- Blood driven into the left and right aortic sinuses enters into the ostia of the coronary arteries.
Discuss the muscles and ligaments involved with flexion and extension of the digits of the foot, and relate this to function
- Flexion of the digits, relative to extension, is more specific because of the independence of flexor tendons relative to extensor tendons
- The primary flexors of the toes include the flexor hallucis longus and brevis, the flexor digitorum longus and brevis, and flexor digiti mini
- Flexor Hallucis longus - inserts at base of distal phalynx of digit 1
- flexes the IP joint plus the MP and ankle joint
- Origin from posterior compartment of leg - intersseous membrane and fibula
- crosses ankle inferior to sustentaculum tali and within flexor sheath
- receives guidance from the sesamoid bones within the lateral and medial heads of the flexor digitorum brevis
- Flexor hallucis brevis - inserts at base of proximal phalanx of digit 1
- flexes the MP joint
- lateral and medial head each host a sesamoid bone near the head of the first metatarsal
- sesamoid bones provide a "groove" to guide the tendon of flexor hallucis longus toward the distal phalanx
- sesamoid bones provide site of attachment for the abductor hallucis and the adductor hallucis
- Flexor digitorum longus - inserts on the base of the distal phalanx of digits 2-4
- flexes the distal IP joint plus the proximal IP, MP, and ankle
- lumbricals arise from the lateral sides of the the tendons - extend IP and flex MP
- origin from the posterior compartment of the leg - tibia and interosseous membrane
- crosses ankle superior to sustentaculum tali and within the flexor sheath
- Flexor digitorum brevis - inserts at the base of the middle phalanx of digits 2-4
- flexes the proximal IP joint plus the MP joint
- origin from the calcaneous - intrinsic to the foot
- tendons are approximated to planter surface of flexor digitorum longus
- tendon splits and inserts onto the sides of the base of the middle phalanx
- the tendon of flexor digitorum longus passes through the split tendon without tethering to the flexor digitorum brevis
- independent action at the distal and proximal IP joint is preserved relative to the extensors (extensor hood)
- Flexor digiti minimi - inserts at the base of the middle phalanx of digit 5
- flexes the proximal IP joint plus the MP joint
- intrinsic to the foot
- The primary extensors of the toes include extensor hallucis longus and brevis, and extensor digitorum longus and brevis
- Extensor hallucis longus - inserts on the distal and proximal phalanges of digit 1
- extends the IP joint plus the MP joint plus the ankle
- origin from the anterior compartment of the leg - tibia and interosseous membrane
- stabilized by the superior and inferior retinaculae
- tendone receives a lateral attachement at the level of the head of the first metatarsal from extensor hallucis brevis
- The tendons of extensor hallucis longus and brevis are tethered to each other and can not act independently.
- Extensor hallucis brevis - inserts on the distal and proximal phalanges of digit 1 (via tendon of extensor hallucis longus)
- extends the IP and MP joint
- instrinsic to the dorsum of the foot
- tendon attaches to lateral side of the tendon of extensor hallucis longus or to the proximal phalanx
- origin is from the anterolateral aspect of the calcaneous
- has been considered a named slip of extensor digitorum brevis
- Extensor digitorum longus - inserts on the bases of the middle and distal phalanges of digits 2-5 be way of the extensor hood
- extends the distal and proximal IP joints plus the MP and the ankle joints
- origin from the anterior compartment of the leg - interosseous membrane and the fibula
- stabilized by the superior and inferior extensor retinaculae
- tendons receive lateral attachments from the extensor digitorum brevis on digits 2-4 at level of head of metatarsal
- the combined tendons of the extensor digitorum longus and brevis contribute to the extensor hood
- extensor hood has a center insertion on the middle phalanx and sends two lateral bands to insert on the sides of the base of the distal phalanx
- extensor hood also receives fibrous contributions from the lumbricals and the interossei
- The extensor digitorum longus and brevis are tethered to each other by the extensor hood and can not act independently
- Extensor digitorum brevis - inserts on the extensor hood and, thus, to the bases of the middle and distal phalanges of digits 2-4 (not 5)
- extends the distal and proximal IP joints plus the MP
- origin is from the anterolateral aspect of the calcaneous
- tedons attach to the extensor at the lateral aspect of the extensor digitorum longus at the level of the head of the metatarsals
- Additional comments
- Mesotendons (vincula) drived from tendon sheaths provide vascular and nervous supply to the distal flexor tendons
- It is the relative independence of the flexor tendons and the unique action of the lumbricals that permit greater specificity of flexion.
- The deep and superficial transverse metatarsal ligaments stabilize the heads of the metatarsals and contribute to fine movement.
- Collateral ligaments at the MP and IP joints stablize flexion and extension.
Review the boundaries (6 in number) and contents (vasculature, nerves,
lymphatics) of the femoral triangle. State the relationship of structures
entering and leaving this region. (12 pts)
superior boundary: Inguinal ligament spanning the anterior superior iliac
spine and pubic tubercle (including a figure would help)
contents of the muscular and vascular lacunae enter the femoral triangle
The vascular lacuna is located posterior to the inguinal ligament, medial
to the iliopectineal arch, lateral to the lacunar ligament, and anterior
to the pectineal fascia.
The contents include, from the lateral to medial, the femoral artery, the
femoral vein, and the femoral canal.
These contents are contained within compartments of the femoral sheath.
These compartments are separated by septa that run between the inguinal
ligament and the pectineal fascia.
Femoral hernias occur in this region.
abdominal viscera may enter the femoral canal through the femoral ring.
posterior to inguinal ligament and lateral to iliopectineal arch
femoral nerve enters femoral triangle deep to iliacus fascia
lateral femoral cutaneous nerve enters femoral triangle lateral to femoral
nerve and near anterior superior iliac spine
lateral boundary: sartious
medial boundary: adductor longus
lateral femoral circumflex a/v exits laterally deep to sartious and between
rectus femoris and vasti
inferior boundary: adductor canal at the apex
profunda femoral a/v exits posteromedial deep to super border of adductor
longus and continues between adductor longus and adductor magnus
posterior boundary: iliopsoas, pectineus, and possibly parts of adductor
brevis and adductor longus
At the apex of the femoral triangle is the beginning of the adductor canal.
The femoral artery and vein, and the saphenous nerve enter the adductor
artery anterior to vein - note: this relation betrays relation of popliteal
The adductor canal is bounded anteromedially by the sartorius muscle. Anterolaterally,
it is bounded by the vastus medialis. Posteriorly it is bounded by
adductor longus and adductor magnus.
nerve to vastus intermedius enters adductor canal
anterior boundary: fascia lata and saphenous hiatus (show relations fig)
the medial femoral circumflex a/v exits between iliopsoas and pectineus
the deep femoral artery exits between iliopsoas and adductor longus
the contents of the cribriform fascia exit the femoral triangle at this
superficial/external pudendal a/v
superficial epigastric a/v
superficial circumflex iliac a/v
the great saphenous vein
anterior femoral cutaneous nn pierce fascia lata anterior.
The saphenous hiatus
is a specialization of the fascia lata located in the anteromedial thigh
just inferior to the inguinal ligament and superficial to the femoral sheath.
The lateral margin overlies the femoral artery. The medial aspect
overlies the femoral canal. Superiorly is the inguinal ligament.
Approximately 2cm inferior to the inguinal ligament is the inferior cornu
over which the great saphenous vein forms an arch as it leaves superficial
fascia and enters the femoral vein. Notable tributaries of the great
saphenous vein within the saphenous hiatus are the external pudendal vein
coursing medially, the superficial epigastric vein coursing superiorly,
and the superficial circumflex iliac vein coursing laterally and superiorly.
Accompanying these veins are branches of the femoral artery. These
vessels are piercing through the surrounding cribriform fascia. The
distinct lateral margin of the saphenous hiatus is the falciform edge.
There are superior and inferior borders referred to as the superior and
inferior cornu. Medially, the hiatus is indistinct and blends with
the pectineus fascia. The femoral ring is located immediately deep
to the medial aspect of the saphenous hiatus. A femoral hernia, if
present, can be palpated at this location. Additionally, a femoral
pulse can be located and, thus, easy surgical access to a major artery
or vein is possible.
Lymph funnel shaped lymph channel located in the most medial compartment
of the femoral sheath.
Femoral ring is at the superior opening of this canal.
Formed by an 1.5cm extension of transversalis fascia from the abdominal
cavity into the thigh.
Exposed to superficial fascia by the saphenous hiatus.
Site of femoral hernia
more common in females because of wider pelvic bones and larger femoral
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The Structural Basis of Medical Practice - Human Gross Anatomy
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