---

MBBS 1st Professional Anatomy Exam - Complete Answers

---

Q.1 - Describe Knee Joint (20 Marks)

i. Ligaments

• Continuation of the quadriceps femoris tendon below the patella
• Attached above to the margins and apex of the patella, below to the tibial tuberosity

• Fibular (Lateral) Collateral Ligament - cord-like; from lateral femoral epicondyle above to the lateral surface of the fibular head below; separated from fibrous membrane by a bursa
• Tibial (Medial) Collateral Ligament - broad and flat; from medial femoral epicondyle to the medial margin/surface of the tibia; deep surface is attached to the fibrous membrane and medial meniscus

• Anterior Cruciate Ligament (ACL) - prevents anterior displacement of tibia on femur; attaches from anterior intercondylar area of tibia to lateral wall of femoral intercondylar fossa
• Posterior Cruciate Ligament (PCL) - prevents posterior displacement of tibia on femur; attaches from posterior intercondylar area of tibia to medial wall of femoral intercondylar fossa

---

ii. Intra-articular Structure

• Medial Meniscus - larger, C-shaped; attached at its margin to the capsule and tibial collateral ligament (hence more prone to injury)
• Lateral Meniscus - more circular; not attached to the fibular collateral ligament; more mobile

• Accommodate changes in shape of articular surfaces during movement
• Act as shock absorbers
• Deepen the tibial condyles and improve congruity
• Aid in lubrication and nutrition of articular cartilage

---

iii. Applied Importance

• Meniscal tears - occur during forceful rotation/twisting; patient presents with pain, locking, clicking, and swelling; diagnosed by MRI; treated by arthroscopy
• ACL tear - "anterior drawer sign" positive; patient presents with instability and giving way
• MCL (tibial collateral ligament) tear - most common collateral ligament injury due to its attachment to the medial meniscus
• Prepatellar bursitis ("Housemaid's Knee") - inflammation from repeated kneeling
• Osteoarthritis - commonly affects the knee due to weight-bearing

---

iv. Movements

---

v. Locking and Unlocking of Knee

• As the knee approaches full extension, the femur medially rotates on the tibia
• The articular surfaces change from curved (in flexion) to flat and broader (in extension)
• This tightens ALL associated ligaments
• The body's center of gravity passes anterior to the knee axis in standing
• Result: The knee is "locked" in a stable position with minimal muscle energy required

• Initiated by the popliteus muscle which causes lateral rotation of the femur on the fixed tibia
• This is why popliteus is called "the key to the knee"

---

Q.2 - Describe Lungs Under the Following Headings (20 Marks)

a) External Features

• Conical in shape with an apex, base, three borders (anterior, posterior, inferior) and two surfaces (costal and mediastinal/medial)
• Apex - projects above the first rib and clavicle into the root of the neck (~2.5 cm above the medial 1/3 of clavicle)
• Base - rests on the diaphragm (concave)
• Costal surface - smooth, convex; relates to ribs and intercostal spaces
• Anterior border - thin and sharp; the left lung has the cardiac notch at this border (where the apex of the heart is exposed), continued below as the lingula
• Inferior border - separates costal and diaphragmatic surfaces
• Posterior border - rounded; lies in the paravertebral gutter
• Hilum - depression on the mediastinal surface where the root of lung enters (bronchus, pulmonary artery, pulmonary veins, lymphatics, nerves)

---

b) Well-labeled Diagrams of Mediastinal Surface of Both Lungs

         APEX
          |
    SVC groove      
    Azygos vein groove (arches over root)
    Cardiac impression (right atrium)
    IVC groove
         ↓
    Oesophageal groove (posterior)
    Root of lung (hilum) - contains:
      • Right main bronchus (posterosuperior)
      • Pulmonary artery (superior)
      • Superior + inferior pulmonary veins

• Anterior to hilum: SVC, right atrium
• Posterior to hilum: Oesophagus, azygos vein
• Above hilum: Azygos vein arches over root

---

         APEX
          |
    Subclavian artery groove
    Aortic arch impression (arch groove)
    Descending aorta groove (posterior)
    Cardiac impression (left ventricle - large)
    Root of lung (hilum) - contains:
      • Left main bronchus (inferior)
      • Pulmonary artery (superior/anterior)
      • Superior + inferior pulmonary veins

• Anterior to hilum: Left ventricle (large cardiac impression)
• Posterior to hilum: Descending aorta, oesophagus
• Above hilum: Aortic arch, left subclavian artery

---

c) Bronchopulmonary Segments of Both Lungs

---

Q.3 - Brief Answer Questions (5×6 = 30 Marks)

a) Right Atrium

1. Superior vena cava - upper posterior part
2. Inferior vena cava - lower posterior part (with valve of IVC = Eustachian valve)
3. Coronary sinus - between IVC and right AV orifice (with Thebesian valve)

• Posterior smooth part (sinus venarum) - derived from right horn of sinus venosus; walls are smooth
• Anterior rough part (atrium proper + auricle) - contains musculi pectinati (pectinate muscles) arranged like teeth of a comb

• Fossa ovalis - oval depression in interatrial septum; remnant of fetal foramen ovale; surrounded by muscular ridge called limbus fossae ovalis (annulus ovalis)
• Right auricle - ear-shaped muscular pouch overlapping the ascending aorta
• AV node - lies at the base of the interatrial septum near the opening of coronary sinus
• Right atrioventricular orifice - closed by tricuspid valve during systole

---

b) Azygos System of Veins

• Arises at L1/L2 from union of right ascending lumbar vein + right subcostal vein
• Enters thorax through aortic hiatus or posterior to right crus of diaphragm
• Ascends in posterior mediastinum (right of thoracic duct)
• At T4 level, arches anteriorly over the root of the right lung → joins SVC
• Tributaries: Right posterior intercostal veins (5th-11th), right superior intercostal vein (2nd-4th), hemiazygos, accessory hemiazygos, oesophageal, pericardial, mediastinal, right bronchial veins

• Arises from left ascending lumbar + left subcostal vein
• Ascends to T9, then crosses the midline at T9 to drain into azygos
• Receives lower 4-5 left posterior intercostal veins and left subcostal vein

• Descends from T4 to T8/T9
• Crosses to drain into azygos or hemiazygos
• Receives 4th-8th left posterior intercostal veins

---

c) Fertilization and Its Effects

1. Capacitation of sperm in female genital tract (~7 hours)
2. Sperm penetrates corona radiata (hyaluronidase)
3. Sperm binds to zona pellucida (ZP3 receptor) → acrosome reaction releases enzymes
4. Sperm penetrates zona pellucida → fuses with oocyte plasma membrane
5. Cortical reaction → zona reaction prevents polyspermy
6. Secondary oocyte completes second meiotic division → mature ovum + second polar body
7. Male and female pronuclei form → fuse → zygote (2n = 46 chromosomes)

1. Completion of 2nd meiotic division of the secondary oocyte
2. Prevention of polyspermy (zona reaction)
3. Restoration of diploid number (46 chromosomes)
4. Determination of genetic sex of embryo (X or Y from sperm)
5. Initiation of cleavage (mitotic divisions)
6. Metabolic activation of the ovum

---

d) Popliteal Fossa

• Superomedial - Semimembranosus and semitendinosus
• Superolateral - Biceps femoris
• Inferomedial - Medial head of gastrocnemius
• Inferolateral - Lateral head of gastrocnemius + plantaris
• Floor (deep): Popliteal surface of femur, posterior capsule of knee, popliteus muscle (below)
• Roof: Skin + fascia (popliteal fascia)

1. Popliteal lymph nodes
2. Tibial nerve (most superficial)
3. Common fibular (peroneal) nerve (lateral)
4. Popliteal vein
5. Popliteal artery (deepest)

• Popliteal aneurysm - most common peripheral aneurysm; presents as pulsatile swelling
• Baker's cyst - herniation of synovial membrane through posterior capsule; fluctuant swelling in popliteal fossa

---

Q.4 - Short Answer Questions (1×10 = 10 Marks)

a) Hamstring Muscle

• Origin: Ischial tuberosity (long head of biceps from lateral lip, others from medial lip); short head of biceps from linea aspera
• Insertion: Biceps → head of fibula; Semitendinosus → upper medial tibia (pes anserinus); Semimembranosus → posterior medial tibial condyle
• Actions: Extend hip, flex knee; semimembranosus and semitendinosus medially rotate leg
• Nerve supply: Tibial division of sciatic nerve (except short head of biceps → common fibular division)

b) Angle of Louis (Sternal Angle)

• Junction between manubrium and body of sternum at T4-T5 level
• Landmarks: Level of 2nd rib articulation, bifurcation of trachea, carina, arch of aorta begins and ends, ligamentum arteriosum, superior mediastinum boundary below

c) Iliotibial Tract

• Thickened band of fascia lata on the lateral thigh
• Formed by tensor fasciae latae + gluteus maximus
• Runs from iliac crest to Gerdy's tubercle (lateral condyle of tibia)
• Applied: Iliotibial band syndrome (runner's knee); tight ITB in TFL weakness

d) Angle of Louis - (see above - same as b)

e) Popliteus Muscle

• Origin: Lateral femoral condyle + posterior horn of lateral meniscus
• Insertion: Posterior surface of tibia above soleal line
• Action: "Unlocks" the knee - initiates lateral rotation of femur on fixed tibia to begin flexion; also medially rotates tibia on fixed femur
• Nerve: Tibial nerve (L4, L5, S1)
• Called "the key to the knee"

f) Types and Histology of Cartilages

• Chondrocytes lie in lacunae (cell spaces)
• Surrounded by territorial matrix (dark, rich in proteoglycans) and interterritorial matrix (lighter)
• Groups of chondrocytes = isogenous groups (cell nests) from mitotic division
• Perichondrium = outer fibrous layer + inner chondrogenic layer (contains chondroblasts)
• Appositional growth (from perichondrium) and interstitial growth (from within)

g) Typical Intercostal Space

• Contains intercostal muscles (external, internal, innermost), neurovascular bundle
• VAN order (superior to inferior at angle): Vein, Artery, Nerve
• Intercostal nerve runs in the costal groove of the rib above
• Applied: During thoracocentesis, needle inserted above the upper border of lower rib to avoid VAN bundle

h) Adductor Canal (Hunter's Canal)

• Triangular intermuscular tunnel in middle 1/3 of medial thigh
• Boundaries: Anterolateral - vastus medialis; posterior - adductor longus/magnus; roof - sartorius (and fascia)
• Contents: Femoral artery, femoral vein, saphenous nerve, nerve to vastus medialis, descending genicular artery
• Applied: Femoral artery adductor canal block (ACB) for knee analgesia; femoral artery may be occluded here in peripheral vascular disease

i) Functions of Placenta

1. Nutrition - transfer of glucose, amino acids, fatty acids to fetus
2. Respiration - O2 transfer to fetus, CO2 removal
3. Excretion - transfer of urea, bilirubin to maternal blood
4. Hormonal - produces hCG, hPL (somatomammotropin), oestrogen, progesterone
5. Immunological - transfers maternal IgG antibodies (passive immunity); acts as partial barrier
6. Barrier function - protects fetus from some drugs/microorganisms (though incomplete)

j) Histology of Bone (Secondary/Lamellar Bone)

• Osteon (Haversian system) = basic structural unit
• Central Haversian canal contains blood vessels and nerves
• Lamellae - concentric rings of mineralized matrix (hydroxyapatite + collagen type I) around Haversian canal
• Osteocytes in lacunae connected by canaliculi (contain osteocyte processes)
• Cement lines - boundary of each osteon
• Volkmann's canals - horizontal channels connecting Haversian canals
• Interstitial lamellae - remnants of old osteons
• Periosteal lamellae - outermost; attached to periosteum
• Endosteal lamellae - innermost; adjacent to marrow cavity

---