The Definitions Bank
Ten terms, three marks each, three minutes each. This is the most predictable thirty marks on the paper — and the easiest to lose, because a definition is graded on structure, not on how much you know.
How a three-mark definition is actually marked
Here is the thing almost every student gets wrong about this section. You are not being asked what you know about the femoral triangle. You are being asked to produce a specific object: a short paragraph with a fixed shape. The examiner has a mark scheme in front of them with three or four boxes on it, and they are ticking boxes. Write beautifully around the boxes and you score nothing.
Nearly every term in this subject is a space — a triangle, a canal, a fissure, a foramen, a sheath, a recess. And every space has the same two properties: walls, and whatever is inside the walls. So a full-mark answer is almost always the same three moves:
- Say what kind of thing it is, and where. One sentence. "A wedge-shaped depression at the junction of the anterior abdominal wall and the thigh."
- Give the boundaries — named, and labelled by direction. Not "sartorius and adductor longus", but "laterally the medial margin of sartorius, medially the medial margin of adductor longus".
- Give the contents, in order. And say which direction you are reading them in.
That last point is worth a mark on its own and costs you nothing. Your TMU slides list the femoral triangle's contents medial-to-lateral; Gray's lists them lateral-to-medial. Both are right. A student who writes "femoral nerve, artery, vein" without saying from lateral to medial has written something that is ambiguous, and an examiner reading fast may mark it wrong. Six words of insurance.
True, fluent, and mostly worthless. No boundaries at all — that is half the mark scheme gone. No order to the contents. The clinical sentence earns nothing because it was not asked for.
Same knowledge. Shaped to the mark scheme. Forty seconds to write.
Before you leave a definition in the exam, read it back and ask: could a surgeon find this space from what I have written? If the walls are all named and the contents are in order, yes. If not, you have written a description, not a definition.
- What are the three moves of a full-mark definition? → What-and-where · boundaries with directions · contents in a stated order
- Why state the direction you are reading contents in? → TMU slides and Gray's read opposite ways; without it your answer is ambiguous
- Should you add clinical significance? → Only if asked, or if you have time — it earns nothing when the question says "define"
When your slides and your textbook disagree
Several structures in this course have two names. TMU teaches the Chinese and continental European terminology; Gray's and Snell's use the Anglo-American one. Neither is wrong, but you must write the one the examiner is expecting, and you must recognise the other when you read around the subject.
Terms marked TMU term below do not appear under that name in Gray's or Snell's at all. They are cited to the TMU lecture or to a real past paper — never to an invented textbook page. Write these ones the TMU way.
| TMU / your slides | Gray's & Snell's | Note |
|---|---|---|
| Malleolar canal | Tarsal tunnel | Identical structure |
| Scalene fissure | Interscalene triangle | Identical structure |
| Inguinal triangle | Hesselbach's triangle | Gray's uses both names |
| Gall bladder triangle | Calot's / cystohepatic triangle | Not named in Gray's or Snell's |
| Lacuna musculorum / vasorum | — no equivalent name — | Continental term; TMU slide only |
| Supra- / infrapiriform foramen | "above / below piriformis" | Gray's describes but does not name them |
| Venous angle | — described unnamed — | IJV + subclavian vein junction |
The bank — drill it
Cards start closed on purpose. Read the term, say the boundaries and contents out loud, then open it and check. Mark each one honestly — the counter at the top only helps you if it tells the truth.
A wedge-shaped depression at the junction of the anterior abdominal wall and the thigh.
- Base (superior): inguinal ligament
- Lateral: medial margin of sartorius
- Medial: medial margin of adductor longus
- Apex: points inferiorly, continuous with the adductor canal
- Floor: iliopsoas laterally; pectineus and adductor longus medially
- Roof: fascia lata, pierced by the saphenous opening
Lateral → medial: femoral nerve · femoral artery · femoral vein · lymphatics in the femoral canal.
A triangular fascial tunnel in the medial third of the thigh, running from the apex of the femoral triangle to the adductor hiatus.
- Anterolateral: vastus medialis
- Posterior: adductor longus above, adductor magnus below
- Roof: fibrous membrane covered by sartorius
Anterior → posterior: saphenous nerve · femoral artery · femoral vein. The saphenous nerve leaves to become cutaneous; the vessels continue through the adductor hiatus as the popliteal vessels.
A funnel-shaped sleeve of fascia around the femoral vessels below the inguinal ligament, formed by downward prolongation of the transversalis fascia in front and the iliac fascia behind.
- Lateral compartment: femoral artery
- Intermediate compartment: femoral vein
- Medial compartment: the femoral canal (lymphatics and fat)
⚠️ The femoral nerve is NOT in the sheath — it lies lateral to and outside it. A content of the triangle, not of the sheath.
The most medial, conical compartment of the femoral sheath, about 1.25 cm long.
- Its upper opening is the femoral ring, bounded:
- Anteriorly: inguinal ligament
- Posteriorly: pecten pubis
- Medially: lacunar ligament
- Laterally: femoral vein
Lymphatic vessels, a lymph node (of Cloquet) and fat. Clinical: the route of a femoral hernia, which appears below and lateral to the pubic tubercle and strangulates readily because the ring is small and rigid.
The lateral of the two compartments beneath the inguinal ligament.
- Anteriorly: inguinal ligament
- Laterally: ilium
- Medially: iliopectineal arch
Iliopsoas muscle · femoral nerve · lateral femoral cutaneous nerve.
The medial of the two compartments beneath the inguinal ligament.
- Anteriorly: inguinal ligament
- Laterally: iliopectineal arch
- Medially: lacunar ligament
- Posteriorly: pecten pubis
Femoral artery · femoral vein · femoral canal with its lymphatics.
An oval aperture in the fascia lata just inferior to the medial end of the inguinal ligament.
- Its margin is the free medial edge of the fascia lata, which spirals around the lateral side of the great saphenous vein and passes medially beneath the femoral vein to attach to the pectineal line
Transmits the great saphenous vein from the superficial fascia to join the femoral vein.
An opening in the lower attachment of adductor magnus, between its adductor and hamstring portions.
- Bounded by the adductor and hamstring parts of adductor magnus and the shaft of the femur
Transmits the femoral artery and vein from the adductor canal into the popliteal fossa — the point at which they are renamed the popliteal vessels.
The opening between the upper border of piriformis and the upper margin of the greater sciatic foramen.
- Above: upper margin of the greater sciatic foramen
- Below: upper border of piriformis
Lateral → medial (3): superior gluteal nerve · superior gluteal artery · superior gluteal vein.
The opening between the lower border of piriformis and the sacrospinous ligament.
- Above: lower border of piriformis
- Below: sacrospinous ligament / upper margin of the lesser sciatic foramen
Lateral → medial (8): sciatic nerve · posterior femoral cutaneous nerve · inferior gluteal nerve · inferior gluteal artery · inferior gluteal vein · internal pudendal artery · internal pudendal vein · pudendal nerve.
Group them: to the thigh (1–2) · to the buttock (3–5) · to the perineum (6–8).
The opening formed when the sacrospinous ligament bridges the greater sciatic notch of the hip bone.
- Anterolaterally: greater sciatic notch of the ilium
- Posteromedially: sacrotuberous ligament
- Inferiorly: sacrospinous ligament and ischial spine
The main route between the pelvic cavity and the gluteal region. Subdivided by piriformis into the suprapiriform and infrapiriform foramina.
The opening formed when the sacrotuberous ligament bridges the lesser sciatic notch.
- Anteriorly: lesser sciatic notch of the ischium
- Superiorly: sacrospinous ligament and ischial spine
- Posteriorly: sacrotuberous ligament
Tendon of obturator internus and its nerve · the pudendal nerve and internal pudendal vessels re-entering the pelvis to reach the perineum.
A diamond-shaped space behind the knee joint, between the muscles of the posterior compartments of the thigh and leg.
- Superolateral: biceps femoris
- Superomedial: semitendinosus and semimembranosus
- Inferolateral: lateral head of gastrocnemius (with plantaris)
- Inferomedial: medial head of gastrocnemius
- Floor: knee joint capsule and adjacent femur and tibia; popliteus below
- Roof: deep fascia, continuous with fascia lata above and deep fascia of the leg below
Superficial → deep: tibial nerve and common fibular nerve · popliteal vein · popliteal artery. Plus popliteal lymph nodes and fat.
An osteofibrous canal on the posteromedial side of the ankle — the gateway from the posterior compartment of the leg into the sole.
- Anteriorly / above: medial malleolus of the tibia
- Laterally / floor: medial surface of the calcaneus and talus
- Roof: flexor retinaculum
Anterior → posterior (5): tendon of tibialis posterior · tendon of flexor digitorum longus · posterior tibial artery and veins · tibial nerve · tendon of flexor hallucis longus.
Tom, Dick And Very Nervous Harry.
An intermuscular space located immediately below the glenohumeral (shoulder) joint.
- Above: subscapularis and teres minor, and the capsule of the shoulder joint
- Below: teres major
- Medially: long head of triceps
- Laterally: surgical neck of the humerus
Axillary nerve and the posterior circumflex humeral artery (and vein).
Clinical: the axillary nerve lies against the surgical neck here — a fracture at that site, or a shoulder dislocation, injures it, paralysing deltoid and numbing the 'regimental badge' area.
The smaller intermuscular space medial to the quadrangular space, in the scapular region.
- Above: teres minor
- Below: teres major
- Laterally: long head of triceps
Circumflex scapular artery — a branch of the subscapular artery, contributing to the scapular anastomosis.
A fascial sleeve that is a downward prolongation of the prevertebral layer of deep cervical fascia, extending over the first rib into the axilla.
- Derived from the prevertebral fascia of the neck
Encloses the axillary vessels and the brachial plexus.
Clinical: this is what makes a brachial plexus block possible — the distal sheath is closed with finger pressure and anaesthetic injected proximally is massaged along it.
A triangular depression on the anterior aspect of the elbow, conveying major structures between the arm and forearm.
- Laterally: brachioradialis
- Medially: pronator teres
- Base (superiorly): an imaginary line between the two epicondyles of the humerus
- Floor: brachialis and supinator
- Roof: deep fascia reinforced by the bicipital aponeurosis
Lateral → medial: tendon of biceps brachii · brachial artery · median nerve. The radial nerve lies deep in the lateral part.
A condensation of the deep cervical fascia receiving a contribution from all three of its layers, surrounding the major neurovascular bundle on each side of the neck.
- Formed by contributions from the investing, pretracheal and prevertebral layers of deep cervical fascia
Common and internal carotid arteries medially · internal jugular vein laterally · vagus nerve [X] posteriorly, in the angle between the two vessels. Deep cervical lymph nodes lie along it.
A dilation of the terminal part of the common carotid artery and the beginning of the internal carotid artery, at the bifurcation in the carotid triangle.
- Located at the bifurcation of the common carotid artery
Contains baroreceptors that monitor changes in blood pressure, innervated by a branch of the glossopharyngeal nerve [IX].
Clinical: pressure here can slow the heart — carotid sinus massage, and the reason a tight collar can cause syncope in the susceptible.
A small accumulation of receptors in the region of the carotid bifurcation.
- Lies in the fork of the bifurcation of the common carotid artery
Chemoreceptors detecting changes in blood chemistry, primarily oxygen content. Innervated by branches of both the glossopharyngeal [IX] and vagus [X] nerves.
A triangular gap in the root of the neck through which structures pass from the neck into the upper limb.
- Anteriorly: scalenus anterior
- Posteriorly: scalenus medius
- Inferiorly: first rib
Subclavian artery (third part) and the roots of the brachial plexus.
⚠️ The subclavian vein passes in front of scalenus anterior and is therefore not in the fissure — a favourite trap.
Clinical: narrowing of this gap causes thoracic outlet syndrome.
The angle formed by the junction of the internal jugular vein and the subclavian vein on each side, where they unite to form the brachiocephalic vein.
- Between the internal jugular vein and the subclavian vein
The thoracic duct opens into the left venous angle; the right lymphatic duct opens into the right venous angle.
Clinical: this is why left supraclavicular (Virchow's) node enlargement signals abdominal malignancy.
A slit-like potential space of the pleural cavity where the costal pleura becomes continuous with the diaphragmatic pleura.
- Between the costal and diaphragmatic parts of the parietal pleura
Normally empty — the lung does not fill it, even in deep inspiration.
Clinical significance: it is the lowest part of the pleural cavity, so fluid (a pleural effusion) collects here first, and it is the site chosen for pleural aspiration / chest drain insertion.
A dilated lymphatic sac at the lower end of the thoracic duct, lying in the abdomen.
- Lies on the right side of the abdominal aorta, in front of the bodies of the upper lumbar vertebrae (about L1–L2)
Receives the intestinal trunk and the right and left lumbar trunks, and drains upward as the thoracic duct, which passes through the aortic hiatus of the diaphragm.
A triangular area of the lower anterior abdominal wall which is a site of weakness.
- Laterally: inferior epigastric artery
- Medially: lateral border of rectus abdominis
- Inferiorly: inguinal ligament
No structures pass through it — it is defined by its weakness.
Clinical: a direct inguinal hernia bulges forward through this triangle, medial to the inferior epigastric vessels. An indirect hernia enters the deep ring lateral to those vessels — that single relationship distinguishes the two.
A fibrous median raphe running in the midline of the anterior abdominal wall from the xiphoid process to the pubic symphysis.
- Formed by the interlacing aponeuroses of the external oblique, internal oblique and transversus abdominis of both sides, separating the two rectus abdominis muscles
Pierced above the umbilicus by little except small vessels — which is why it is chosen for a midline laparotomy: the incision is relatively bloodless and avascular, and no nerve is divided.
A small triangular region on the inferior surface of the liver, exposed during cholecystectomy.
- Right (laterally): cystic duct
- Left (medially): common hepatic duct
- Above: inferior surface of the liver
The cystic artery (usually a branch of the right hepatic artery), the right hepatic artery, and a cystic lymph node.
Clinical: the surgeon must identify the cystic artery here before clipping it — the commonest cause of bile duct injury in laparoscopic cholecystectomy is mistaking the common bile duct for the cystic duct in this triangle.
A nerve trunk linking the lumbar plexus to the sacral plexus.
- Formed by part of the anterior ramus of the fourth lumbar nerve emerging from the medial border of psoas major, joining the anterior ramus of the fifth lumbar nerve
Descends into the pelvis in front of the sacroiliac joint and joins the sacral plexus — the anatomical bridge that lets L4 and L5 fibres reach the sciatic nerve.