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NKP SALVE INSTITUTE OF MEDICAL SCIENCES

ANATOMY - 1ST TERMINAL EXAMINATION | SECTION B

Model Answers (Target: 80/100)

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Q.NO. 2 - BRACHIAL PLEXUS (12 Marks)

i. Formation (3 Marks)

• It may receive small contributions from C4 (pre-fixed type) or T2 (post-fixed type).
• It originates between the anterior and middle scalene muscles in the neck (posterior triangle).
• It then passes over the 1st rib and descends into the axilla.

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ii. Diagram (3 Marks)

ROOTS      TRUNKS         DIVISIONS      CORDS         TERMINAL BRANCHES

C5 ─┐
    ├─── Superior Trunk ─ Anterior  ──┐
C6 ─┘                    Posterior ─┐ ├─ LATERAL CORD ─ Musculocutaneous N.
                                   │ │                 ─ Lateral root of Median N.
C7 ──── Middle Trunk  ─  Anterior  ─┘ │
                         Posterior ─┐ │
C8 ─┐                              │ ├─ POSTERIOR CORD ─ Axillary N.
    ├─── Inferior Trunk ─ Anterior ─┐ │ │                ─ Radial N.
T1 ─┘                   Posterior ─┘ │                  ─ Upper/Lower Subscapular N.
                                     │                  ─ Thoracodorsal N.
                                     └─ MEDIAL CORD  ─  Ulnar N.
                                                      ─  Medial root of Median N.
                                                      ─  Medial cutaneous N. of arm
                                                      ─  Medial cutaneous N. of forearm

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iii. Branches with Root Values (3 Marks)

From ROOTS:

From TRUNKS:

From LATERAL CORD:

From MEDIAL CORD:

From POSTERIOR CORD:

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iv. Applied Anatomy (3 Marks)

1. Erb's Palsy (Upper type - C5, C6 injury)

• Caused by forceful separation of head and shoulder (e.g., difficult delivery, motorcycle accident).
• Position: "Waiter's tip" - arm adducted, medially rotated, elbow extended, forearm pronated, wrist flexed.
• Muscles affected: Deltoid, supraspinatus, infraspinatus, biceps, brachialis, brachioradialis.

2. Klumpke's Palsy (Lower type - C8, T1 injury)

• Caused by forceful abduction of the arm (e.g., catching a branch during a fall).
• Position: "Claw hand" - intrinsic muscles of hand paralyzed.
• Horner's syndrome may occur (T1 involvement affecting sympathetic fibers).

3. Thoracic Outlet Syndrome

• Compression of the inferior trunk (C8, T1) between cervical rib or scalenus anterior.
• Pain and tingling along medial aspect of arm and hand (ulnar distribution).

4. Saturday Night Palsy / Wrist Drop

• Radial nerve injury (posterior cord) in spiral groove of humerus.
• Wrist drop: inability to extend wrist and fingers.

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Q.NO. 3 - SHORT ANSWER REASONING QUESTIONS (20 Marks)

A. Why is 2nd week of development known as "week of twos"? (4 Marks)

1. 2 layers of embryonic disc (Bilaminar disc): Epiblast (columnar cells - future ectoderm) and Hypoblast (cuboidal cells).
2. 2 cavities form:
   • Amniotic cavity (from epiblast)
   • Primary yolk sac / exocoelomic cyst (from hypoblast)
3. 2 layers of trophoblast:
   • Cytotrophoblast (inner, mononucleated, mitotically active)
   • Syncytiotrophoblast (outer, multinucleated, invasive)
4. 2 layers of extraembryonic mesoderm:
   • Somatic (parietal) mesoderm
   • Splanchnic (visceral) mesoderm
5. 2 components of extraembryonic coelom (chorionic cavity) form.
6. Prochordal plate marks the future cranial end (also seen in this week).

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B. Why does hyaline cartilage matrix appear homogeneous, and why is it called "hyaline"? (4 Marks)

• Type II collagen fibers - these have the same refractive index as the ground substance (chondroitin sulfate, keratan sulfate, hyaluronic acid).
• Because light passes through collagen and ground substance at the same speed, the collagen fibers are invisible under light microscopy.
• This gives the matrix a uniform, glassy, translucent appearance with no visible fibrous structure - hence it appears homogeneous.

• The word "hyaline" is derived from the Greek word "hyalos" meaning glass.
• The cartilage has a glassy, translucent, bluish-white appearance on gross examination.
• This characteristic translucent appearance (due to the invisible collagen fibers in ground substance) gives it the name "hyaline."

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C. Why is the median cubital vein preferred for venipuncture in the cubital fossa? (4 Marks)

1. Superficial location: It lies in the superficial fascia of the cubital fossa, making it easily visible and palpable.
2. Large caliber and relatively fixed: It is a large, reasonably consistent vein that does not roll away easily.
3. Relatively immobile: It is tethered by the bicipital aponeurosis (lacertus fibrosus) which lies deep to it, preventing rolling.
4. Safe anatomical relations: The bicipital aponeurosis separates the vein from the brachial artery and median nerve lying deep in the cubital fossa. This prevents accidental puncture of the artery or nerve.
5. Connects cephalic and basilic veins: It is a reliable communicating vein that is consistently present.
6. Easily accessible: The elbow crease is a natural landmark that is easy to identify.

Clinical note: The medial approach (near basilic vein) should be avoided because the medial cutaneous nerve of forearm lies near the basilic vein and can be accidentally punctured.

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D. Anatomical basis for carcinoma of breast spreading to vertebrae and brain (4 Marks)

1. The breast drains via lateral thoracic veins → intercostal veins.
2. Intercostal veins connect directly with Batson's vertebral venous plexus - a valveless, low-pressure network of veins surrounding the vertebral column.
3. Because these veins are valveless, blood (and tumor emboli) can flow in any direction depending on pressure changes (e.g., during coughing, straining, Valsalva maneuver).
4. Tumor cells travel retrogradely into the vertebral venous plexus and reach:
   • Vertebral bodies - causing osteolytic metastases (bone pain, pathological fractures)
   • Continuing upward through basilar venous plexus → dural venous sinuses → brain parenchyma

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E. Why is incidence of femoral hernia higher in females? (4 Marks)

1. Wider female pelvis: The female pelvis is broader (gynecoid type), which means the angle of the femoral canal is wider and the inguinal ligament is set at a wider angle. This creates a relatively larger femoral ring.
2. Wider femoral ring in females: The femoral ring (the opening of the femoral canal) is relatively wider in women compared to men. This is because:
   • The female pelvis is broader.
   • The neck of the femur is more oblique.
   • The femoral vessels occupy less of the femoral sheath diameter relatively.
3. Increased intra-abdominal pressure: Repeated pregnancies increase intra-abdominal pressure, pushing abdominal contents through the femoral ring.
4. Relaxin effect: During pregnancy, the hormone relaxin causes relaxation and laxity of ligaments, widening pelvic joints and making the femoral ring even more patent.
5. Pelvic architecture: The female inguinal ligament is oriented more transversely due to the wider pelvis, making the canal more predisposed to herniation.

Note: Despite higher incidence in females, inguinal hernia is still far more common in both sexes overall. Femoral hernia comprises approximately 20-30% of hernias in women but only 2-5% in men.

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Q.NO. 4 - SHORT ANSWER QUESTIONS (20 Marks | Any 4 of 5)

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Q4-A: Carpal Tunnel Syndrome / Median Nerve (5 Marks)

i. Clinical Condition and Nerve Involved (2 Marks)

• The symptoms (tingling/numbness in lateral 3.5 digits = thumb, index, middle, and lateral half of ring finger + thenar wasting) are classic features of median nerve compression at the wrist.
• Nerve involved: Median nerve (C6, C7, C8, T1) - compressed in the carpal tunnel beneath the flexor retinaculum.
• Hypothyroidism is a known predisposing factor as it causes myxedematous infiltration of the carpal tunnel tissues, increasing pressure on the nerve.

ii. Muscles of the Hand Supplied by Median Nerve (2 Marks)

Note: Thenar wasting occurs because abductor pollicis brevis and opponens pollicis (thenar eminence muscles) are denervated.

iii. Phalen's Test (1 Mark)

• The patient maximally flexes both wrists and holds the dorsal surfaces of both hands together for 60 seconds.
• This increases pressure within the carpal tunnel by narrowing it further.
• Positive test: Reproduction of tingling/numbness in the distribution of the median nerve (lateral 3.5 digits) within 60 seconds.
• Sensitivity ~68%, Specificity ~73%.

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Q4-B: Trendelenburg's Sign / Superior Gluteal Nerve (5 Marks)

i. Nerve Injured (1 Mark)

• This nerve exits through the greater sciatic foramen above the piriformis and supplies the gluteus medius, gluteus minimus, and tensor fasciae latae.
• A bullet in the buttock in the upper gluteal region can damage this nerve.

ii. Muscles Supplied by Superior Gluteal Nerve (2 Marks)

iii. Trendelenburg's Sign (2 Marks)

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Q4-C: "Cadaver is our First Teacher" (5 Marks)

1. First-Hand Anatomical Knowledge

• Cadaveric dissection is the oldest and most authentic method of learning human anatomy, dating back to Vesalius (1543, De Humani Corporis Fabrica).
• It provides direct, tactile, three-dimensional knowledge of the human body that no textbook, diagram, or digital model can fully replicate.

2. Understanding Individual Variations

• Cadavers demonstrate anatomical variations that are common in clinical practice (e.g., variations in brachial plexus, aberrant vessels, accessory muscles).
• Books describe the "standard" anatomy; cadavers show reality.

3. Developing Clinical Skills

• Surgeons learn the relative positions of structures - which vessels lie near which nerves, how deep a structure is, what it looks and feels like.
• This directly translates to safer surgeries.

4. Respect for Human Body

• Dissecting a cadaver instills in the student a deep respect for the human body and the donation that was made.
• It is often considered a student's first patient in their medical journey.

5. Integration of Theory and Practice

• Gross anatomy is the foundation of clinical medicine. Understanding where the radial nerve lies prevents iatrogenic injury. Knowing the femoral triangle helps with safe vascular access.

6. Psychological Preparation

• Exposure to cadavers helps desensitize students to encounters with illness and death - an important aspect of professional formation.

"Before you can care for the living, you must learn from the dead." - The cadaver remains the most honest, detailed, and humbling teacher in medicine.

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Q4-D: Fertilization - Definition, Stages, and Effects (5 Marks)

What is Fertilization?

Stages of Fertilization:

• Sperm penetrates the corona radiata cells surrounding the oocyte using hyaluronidase from the acrosome and mechanical motility.

• Sperm binds to ZP3 glycoprotein of zona pellucida.
• Acrosome reaction occurs: release of acrosin and other hydrolytic enzymes allowing sperm to penetrate through zona pellucida.

• The head and tail of the sperm enter the oocyte cytoplasm.
• The zona reaction (cortical reaction) occurs immediately: cortical granules release enzymes that harden the zona pellucida, forming the fertilization membrane - preventing polyspermy.

• The secondary oocyte (arrested at metaphase II) now completes its 2nd meiotic division producing:
  • A mature ovum (with 23 chromosomes)
  • A 2nd polar body

• Sperm nucleus enlarges to form the male pronucleus (23 chromosomes).
• Oocyte nucleus becomes the female pronucleus (23 chromosomes).

• Nuclear membranes of both pronuclei break down.
• Chromosomes intermingle and the zygote (2n = 46 chromosomes) is formed.

Effects (Significance) of Fertilization:

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Q4-E: Classification of Glands with Examples (5 Marks)

A. Based on Presence or Absence of Ducts:

B. Based on Number of Cells:

C. Based on Structure of Secretory Unit (Morphological):

D. Based on Mode of Secretion:

E. Based on Nature of Secretion:

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Q.NO. 5 - SHORT ANSWER QUESTIONS (28 Marks | Any 4 of 5)

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Q5-A: Femoral Triangle in Detail (7 Marks)

Definition

Boundaries:

Floor:

1. Iliopsoas (lateral part)
2. Pectineus (medial part)
3. Adductor longus (most medial)

Roof:

• Deep fascia of thigh (fascia lata) - with saphenous opening (fossa ovalis) through which great saphenous vein passes to drain into femoral vein.

Contents (Lateral to Medial - mnemonic: N-A-V-E-L):

Important: Femoral nerve is outside the femoral sheath; only femoral artery, vein, and canal are inside the sheath.

Femoral Sheath:

• A funnel-shaped fascial sleeve derived from transversalis fascia (anteriorly) and iliac fascia (posteriorly).
• Contains three compartments:
  • Lateral: Femoral artery
  • Middle: Femoral vein
  • Medial (femoral canal): Lymphatics and fat; site of femoral hernia

Applied Anatomy:

1. Femoral hernia: Enters through the femoral canal (most medial compartment); more common in females due to wider femoral ring.
2. Femoral pulse: Palpated at the midinguinal point (midway between ASIS and pubic symphysis).
3. Cardiac catheterization/angiography: Femoral artery is cannulated in the femoral triangle.
4. Femoral vein catheterization: For CVP monitoring, dialysis.
5. Lymphadenopathy: Deep inguinal nodes enlarge in infections/malignancy of lower limb, perineum, and genitalia.

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Q5-B: Epiphysis - Types and Examples (7 Marks)

Definition

• Ossification of epiphysis typically occurs after birth (except the distal femoral epiphysis, which appears at birth).
• When growth is complete, the epiphyseal plate fuses and the epiphysis merges with the diaphysis (epiphyseal fusion).

Types of Epiphysis:

1. PRESSURE EPIPHYSIS

• Located at the articular ends of bones.
• Transmits the weight/pressure through a joint.
• Covered by articular hyaline cartilage.
• Examples:
  • Head of femur
  • Head of humerus
  • Lower end of radius
  • Condyles of femur and tibia
  • Head of fibula

2. TRACTION EPIPHYSIS (Apophysis)

• Located where tendons or ligaments are attached - not at articular surfaces.
• Subject to traction forces (muscle pull) rather than pressure.
• Examples:
  • Greater and lesser trochanters of femur (gluteus medius/minimus and iliopsoas)
  • Tibial tuberosity (quadriceps via patellar tendon)
  • Medial and lateral epicondyles of humerus
  • Calcaneal tuberosity (Achilles tendon insertion)
  • Coracoid process of scapula

3. ATAVISTIC EPIPHYSIS

• Represents a bone that was separate in ancestors (in evolutionary terms) but has fused in humans; appears as a separate ossification center.
• Examples:
  • Coracoid process of scapula
  • Os trigonum (posterior talus)
  • Styloid process of temporal bone

4. ABERRANT EPIPHYSIS

• An abnormal epiphysis occurring at an unusual site.
• Example:
  • Epiphysis at head of 1st metacarpal (normally at the base)
  • Epiphysis at base of 2nd metacarpal (normally at the head)

Clinical Applications:

1. Osgood-Schlatter disease: Traction apophysitis of tibial tuberosity in adolescent athletes.
2. Slipped capital femoral epiphysis (SCFE): Pressure epiphysis of femoral head slips in obese adolescents.
3. Legg-Calve-Perthes disease: Avascular necrosis of femoral head epiphysis in children.
4. Bone age assessment: Radiographs of hand/wrist assess skeletal maturity by evaluating epiphyseal fusion.

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Q5-C: Deltoid Muscle and Structures Under It (7 Marks)

Deltoid Muscle

Origin (from anterior to posterior - "CAA" = Clavicle, Acromion, Spine of scapula):

Insertion:

• Deltoid tuberosity of the humerus (V-shaped roughened area on lateral surface of middle of humerus)

Nerve Supply:

• Axillary nerve (C5, C6) - from posterior cord of brachial plexus
• The nerve winds around the surgical neck of humerus

Blood Supply:

• Anterior and posterior circumflex humeral arteries (from third part of axillary artery)
• Deltoid branch of thoracoacromial artery

Actions:

Note: Initial 15° of abduction is initiated by supraspinatus; beyond 90° is by trapezius rotating the scapula.

Structures Under the Deltoid (Subdeltoid space / deep to deltoid):

1. Subacromial (subdeltoid) bursa - lies between deltoid and supraspinatus tendon; the most important bursa of the shoulder
2. Supraspinatus tendon (part of rotator cuff)
3. Infraspinatus tendon (part of rotator cuff)
4. Teres minor tendon (part of rotator cuff)
5. Subscapularis tendon (anteriorly, part of rotator cuff)
6. Axillary nerve - passes through the quadrangular space with the posterior circumflex humeral artery
7. Posterior circumflex humeral artery - accompanies axillary nerve
8. Shoulder joint (glenohumeral joint) capsule
9. Long head of biceps tendon (in bicipital groove)

Applied Anatomy:

1. Axillary nerve injury: Surgical neck of humerus fracture → deltoid paralysis → loss of shoulder abduction + loss of sensation over "regimental badge area" (lateral arm).
2. Subdeltoid bursitis: Painful arc syndrome - pain between 60°-120° of abduction.
3. Rotator cuff tear: Supraspinatus most commonly torn; inability to initiate abduction.
4. Deltoid injection: Given in the middle third of the deltoid, avoiding the axillary nerve; volume limit 1-2 mL.

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Q5-D: Popliteal Fossa - Boundaries and Contents (7 Marks)

Definition

Boundaries:

1. Popliteal surface of femur (posterior aspect)
2. Capsule of knee joint + oblique popliteal ligament
3. Popliteus muscle and its fascia (inferior)

• Skin and superficial fascia (containing small saphenous vein + posterior cutaneous nerve of thigh)
• Deep fascia (popliteal fascia) - continuous with fascia lata above and deep fascia of leg below

Contents (from superficial to deep):

• Small saphenous vein - pierces deep fascia in the roof, drains into popliteal vein
• Popliteal lymph nodes (4-6 nodes) - deep to popliteal fascia
• Fat - fills the space
• Posterior capsule of knee joint

Applied Anatomy:

1. Popliteal aneurysm: Most common peripheral artery aneurysm. Pulsatile swelling in popliteal fossa.
2. Baker's cyst (popliteal cyst): Distension of gastrocnemio-semimembranosus bursa; communicates with knee joint in adults.
3. Popliteal artery injury: Supracondylar fracture of femur → limb-threatening ischemia distally.
4. Common fibular nerve injury: At neck of fibula → foot drop (loss of dorsiflexion and eversion).
5. DVT: Popliteal vein is a common site; presents as calf pain and positive Homans' sign.
6. Semimembranosus bursa: Medially situated; communicates with knee joint.

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Q5-E: Wrist Joint (7 Marks)

i. Type

• Proximal component: Concave - distal end of radius + articular disc over distal ulna
• Distal component: Convex - proximal row of carpal bones (scaphoid + lunate + triquetrum)
• Note: The ulna does NOT directly articulate with the carpals (separated by articular disc of inferior radioulnar joint)

ii. Ligaments:

iii. Movements and Muscles:

Note: Radial deviation < ulnar deviation because the radial styloid extends more distally, acting as a bony block.

iv. Applied Anatomy:

1. Colles' fracture: Most common wrist fracture (fall on outstretched hand) - distal radius fracture with dorsal displacement - "dinner fork deformity"; damages radial collateral ligament; median nerve may be involved.
2. Smith's fracture: Reverse Colles' (volar displacement) - "garden spade deformity."
3. Scaphoid fracture: Most common carpal fracture; risk of avascular necrosis (blood supply enters distally).
4. Ganglion cyst: Common on dorsum of wrist; arises from joint capsule or tendon sheath.
5. Carpal tunnel syndrome: Median nerve compressed beneath flexor retinaculum.
6. De Quervain's tenosynovitis: Inflammation of abductor pollicis longus and extensor pollicis brevis at the radial styloid; positive Finkelstein's test.

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EXAM STRATEGY SUMMARY

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• Draw well-labeled diagrams wherever possible (brachial plexus diagram, femoral triangle diagram, popliteal fossa boundaries are expected).
• Use tables for organized presentation of muscles, nerves, ligaments.
• Always include "Applied Anatomy" at the end of Q5 answers - examiners love clinical correlation.
• For Q3 reasoning questions, always explain the "why" - causative reasoning, not just definitions.