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Anatomy & Clinical Exam - Complete Answers

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1. GUNSHOT WOUNDS (Clinical)

• Entry wound: Small, round, with inverted edges; may show "abrasion collar" (zone of abraded skin around entry)
• Exit wound: Larger, irregular, everted (pushed outward); no abrasion collar
• Contact/close range: Soot, tattooing (stippling), singeing of hair present
• Distant: Entry has abrasion collar only; no soot or tattooing

• The missile creates a temporary cavity (stretch) and permanent cavity (crush)
• High-velocity: large temporary cavity - massive tissue destruction
• Low-velocity: small cavitation - injuries limited to direct tract

• Mandatory laparotomy for all has been ABANDONED (negative laparotomy rate was 70-85%)
• Two acceptable approaches:
  1. Serial physical examinations - 91% of patients with occult injury develop symptoms within 6 hours; safe to observe for 24-36 hours
  2. Triple-contrast CT (oral + IV + rectal contrast) - high sensitivity for retroperitoneal injuries; 128-slice CT minimizes missed injuries
• Delayed diagnosis/laparotomy rate with either approach: <5%

• Flank wounds: retroperitoneal colon (ascending/descending), duodenum, kidney, ureter
• Through-and-through anterior wounds: evaluate missile trajectory carefully - oblique tracks may pass through only the abdominal wall fat
• Obesity (>40% of US adults) means many apparent "through-and-through" wounds may not enter the peritoneal cavity

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2. UTERUS - Clinical Case

• Pear-shaped muscular organ; 7-8 cm long, 5-7 cm wide at fundus, 2-3 cm wall thickness
• Parts: Fundus - Body - Isthmus (1 cm) - Cervix
• Layers of the body wall:
  • Perimetrium (outer peritoneal layer)
  • Myometrium (thick smooth muscle - site of fibroids/leiomyomas)
  • Endometrium (inner glandular layer)
• Endometrial layers:
  • Compact layer (surface)
  • Spongy layer (middle, most prominent in secretory phase)
  • Basal layer (deep - NOT shed during menstruation; has its own blood supply)
• Functional layer = compact + spongy = shed during menstruation

• Ectopic pregnancy most often in the ampulla of the uterine tube
• Fibroids (leiomyomas): commonest tumour of uterus; from myometrium; oestrogen-sensitive
• Endometriosis: ectopic endometrium outside uterus; chocolate cysts in ovaries
• Cervical cancer: originates at squamocolumnar junction (transformation zone)
• Retroverted uterus: may cause dyspareunia; impairs fertility rarely
• Lower uterine segment: forms from the isthmus during pregnancy - site of Caesarean section incision (less vascular)

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3. HEART - Clinical

• Beck's triad: hypotension + raised JVP + muffled heart sounds
• Pulsus paradoxus (>10 mmHg fall in systolic BP on inspiration)
• Treatment: pericardiocentesis (needle at left xiphocostal angle, aimed toward left shoulder)

• LAD occlusion: anterior MI, affects anterior LV + anterior 2/3 of IVS
• RCA occlusion: inferior MI, may affect SA node, AV node (since 60% - RCA supplies SA node)
• LCx occlusion: lateral MI (posterior)

• Sternotomy gives access to pericardial cavity
• Heart lies in middle mediastinum
• The phrenic nerve (C3,4,5) runs anterior to hilum - at risk during cardiac surgery

• Apex beat: 5th intercostal space, midclavicular line (left ventricle)
• Auscultation areas: Aortic (2nd ICS right), Pulmonary (2nd ICS left), Tricuspid (lower left sternal border), Mitral (apex)

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4. SALPINGITIS - Clinical Case

• Primary: Neisseria gonorrhoeae, Chlamydia trachomatis
• Secondary (polymicrobial): anaerobes, Mycoplasma, Gram-negatives
• Chlamydia may appear alone or mixed with gonococci

• Fever
• Bilateral lower abdominal pain (key - bilateral distinguishes from appendicitis)
• Adnexal tenderness (cervical excitation test positive)
• Vaginal discharge
• Leukocytosis
• PID develops in 10-20% of women with gonorrhea

• Fertility loss (infertility) - tubal scarring
• Ectopic pregnancy - scarred tubes prevent normal ovum transport
• Intestinal obstruction (adhesions)
• Chronic pelvic pain
• Tubo-ovarian abscess (most serious acute complication)

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5. FEMORAL TRIANGLE

• Base (superior): Inguinal ligament
• Medial border: Medial margin of adductor longus
• Lateral border: Medial margin of sartorius
• Floor: Laterally - iliopsoas; medially - pectineus and adductor longus
• Roof: Fascia lata (with saphenous opening)
• Apex: Points inferiorly → continuous with adductor canal (Hunter's canal)

• N - Femoral Nerve (lateral to sheath)
• A - Femoral Artery
• V - Femoral Vein
• Y - lymphatics (femoral canal - most medial compartment of femoral sheath)

• Lateral: femoral artery
• Intermediate: femoral vein
• Medial (femoral canal): lymphatics - apex = femoral ring (site of femoral hernia)

• More common in women (wider pelvis)
• Passes through femoral ring (medial to femoral vein, lateral to lacunar ligament)
• Exits through saphenous opening
• High rate of strangulation - narrow neck
• Visible/palpable below and lateral to pubic tubercle (cf. inguinal hernia: above and medial)

• Femoral artery pulse palpable just below inguinal ligament, midway between ASIS and pubic symphysis
• Femoral vein - site for central venous access
• Femoral canal - most common site for lymph node metastasis (medial group)

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6. WRONGLY PLACED INTRAMUSCULAR INJECTION - Clinical Case

• Foot drop (common fibular branch affected most - superficially placed)
• Weakness of knee flexion + all muscles below knee
• Sensory loss: lateral leg, dorsum and sole of foot
• Burning pain / causalgia along distribution

• Landmark: Place hand on greater trochanter, index finger on ASIS, middle finger spread toward iliac crest - inject in the triangle formed

• Inadvertent IV injection - rapid systemic absorption
• Abscess formation (poor technique/non-sterile)
• Nerve injury (palsy)
• Oil embolism (if IV injection of oil-based depot)
• Broken needle

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7. DEVELOPMENT OF KIDNEY AND ANOMALIES

• Driven by two reciprocal inductive interactions:
  1. Ureteric bud (outgrowth of mesonephric duct) induces condensation of metanephric mesenchyme
  2. Metanephric mesenchyme induces branching of the ureteric bud
• Ureteric bud forms: ureter, renal pelvis, calyces, collecting tubules
• Metanephric mesenchyme forms: glomeruli, Bowman's capsule, proximal + distal convoluted tubules, Loop of Henle (via mesenchymal-epithelial transition)

• Kidneys develop in pelvis and ascend to lumbar position
• As they ascend, they are successively vascularised by higher aortic sprouts
• Final pair becomes definitive renal arteries

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8. HILUM OF THE LUNG - Clinical Case

• Anterior pulmonary plexus (vagal fibers)
• Pulmonary artery (superior)
• Two pulmonary veins (inferior)
• Bronchus and bronchial vessels (posterior)
• Posterior pulmonary plexus
• Lymph nodes

• Right: an additional upper lobe bronchus (eparterial bronchus) lies superior to the pulmonary artery - "bronchus above the artery"
• Left: pulmonary artery is superior; no eparterial bronchus

• Lymph node enlargement at hilum (hilar lymphadenopathy):
  • Sarcoidosis: bilateral hilar lymphadenopathy (BHL) - "Batman sign" on CXR
  • Primary tuberculosis: Ghon complex = parenchymal focus + hilar node
  • Lymphoma, metastatic carcinoma
• Bronchogenic carcinoma: invades hilar structures causing:
  • Recurrent laryngeal nerve palsy (hoarseness) - left side (longer nerve)
  • SVC syndrome (right-sided tumors compressing SVC)
  • Phrenic nerve palsy: elevated hemidiaphragm
  • Horner syndrome: compression of sympathetic chain
• Root of the lung (hilum) is enclosed in pleura - forms the pulmonary ligament inferiorly, allowing movement of hilar structures

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9. OBTURATOR NERVE

1. Descends along posterior abdominal wall on medial border of psoas
2. Enters pelvic cavity
3. Passes through obturator canal (upper part of obturator foramen)
4. Divides into anterior and posterior branches in the thigh

• Does NOT supply: adductor magnus (hamstring part) = sciatic; pectineus = femoral nerve

1. Obturator hernia - nerve compressed as hernia passes through obturator canal
2. Childbirth - compression on lateral pelvic wall during prolonged labor or instrumental delivery
3. Pelvic surgery - radical hysterectomy, oophorectomy
4. Pelvic fractures
5. Obturator externus abscess

• Weakness of adduction of thigh (wide-based gait, difficulty crossing legs)
• Sensory loss over medial side of upper thigh
• "Howship-Romberg sign" in obturator hernia: pain on medial side of thigh/knee, worsened by medial rotation of hip and relieved by flexion

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10. THORACIC DUCT

• Both lower limbs
• Abdomen and pelvis
• Left half of thorax

1. Enters thorax through aortic hiatus of diaphragm (T12)
2. Ascends in posterior mediastinum between:
   • Thoracic aorta (left)
   • Azygos vein (right)
   • Esophagus (anterior)
3. At T5 level - crosses to the left of midline
4. Ascends left of esophagus through superior mediastinum
5. Enters root of neck to the LEFT of esophagus
6. Arches laterally, posterior to carotid sheath
7. Passes anterior to thyrocervical trunk, phrenic nerve, and vertebral artery
8. Terminates at junction of left internal jugular + left subclavian veins (left venous angle)

• Left jugular trunk (left head + neck)
• Left subclavian trunk (left upper limb)
• Occasionally left bronchomediastinal trunk

• Chylothorax (most important): leakage of chyle into pleural cavity
  • Causes: left-sided surgery (esophagectomy, aortic surgery), trauma, lymphoma
  • Milky/cream-colored pleural fluid; high triglycerides >110 mg/dL
  • Treatment: low-fat diet/TPN, pleurodesis, surgical ligation, or VATS
• Injury during left subclavian venous cannulation - chyle leak
• Chyle leak after neck dissection - left-sided more common (supraclavicular)
• Virchow's node (left supraclavicular): enlarged left supraclavicular lymph node = sentinel node for abdominal/pelvic malignancy (thoracic duct route)

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11. SPLEEN - Clinical Case

• Gastrosplenic ligament (to greater curvature of stomach) - contains short gastric and left gastroepiploic vessels
• Splenorenal (lienorenal) ligament (to left kidney) - contains splenic vessels and tail of pancreas

• Infections: malaria, EBV (infectious mononucleosis), typhoid, kala-azar
• Haematological: lymphoma, leukemia, ITP, hemolytic anemias, polycythemia
• Portal hypertension: liver cirrhosis (congestive splenomegaly)
• Autoimmune: SLE, RA (Felty syndrome)
• Storage disorders: Gaucher's, Niemann-Pick

• Most common solid organ injured in blunt abdominal trauma
• "Kehr's sign": left shoulder tip pain (referred pain from diaphragmatic irritation by blood)
• Delayed rupture may occur days-weeks after trauma (subcapsular hematoma)
• Treatment: splenorrhaphy (repair) if possible; splenectomy if needed
• Post-splenectomy: risk of OPSI (Overwhelming Post-Splenectomy Infection) - especially encapsulated organisms (Pneumococcus, H. influenzae, Meningococcus) → vaccinate + long-term penicillin prophylaxis

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12. KLINEFELTER SYNDROME

• Most common: 47,XXY (90% of cases)
• Others: 48,XXXY; 48,XXYY; 49,XXXXY; mosaics (46,XY/47,XXY)
• Cause: non-disjunction during meiosis (maternal and paternal equally)
• Incidence: ~1 in 660 live male births

• Tall stature with elongated lower body (pubis-to-floor > pubis-to-crown)
• Eunuchoid habitus - abnormally long legs
• Small, firm testes (atrophic; often only 2 cm)
• Azoospermia/infertility (most consistent finding aside from hypogonadism)
• Reduced/absent secondary sex characteristics: sparse beard, sparse pubic hair, small penis
• Gynecomastia
• Low testosterone; elevated FSH/LH
• Cognitive: average to below average; verbal skills most affected

• Tubular hyalinization - "ghost tubules"
• Complete absence of spermatogenesis in most
• Prominent-appearing Leydig cells (due to tubular atrophy + elevated LH)

• Type 2 diabetes / metabolic syndrome
• Mitral valve prolapse (~50% of adults)
• Atrial and ventricular septal defects
• 20-30x increased risk of extragonadal germ cell tumors (especially mediastinal teratomas)
• Increased breast cancer risk
• Autoimmune diseases (SLE)
• Osteoporosis

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13. SEX CHROMATIN (Barr Body)

• In any somatic cell with >1 X chromosome, all but ONE X are inactivated
• Inactivation is random (either maternal or paternal X)
• Occurs early in embryonic life (~day 16)
• Inactivation is permanent and clonally inherited
• The inactive X = Barr body (sex chromatin body)

• In nucleated cells (buccal mucosal cells, neutrophils)
• In neutrophils: Barr body appears as "drumstick" appendage on nuclear lobe

• Quick sex determination from buccal smear
• Screening for sex chromosome aneuploidies
• Replaced largely by karyotyping/FISH but still tested in exams

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14. RIGHT CORONARY ARTERY (RCA)

• Right dominant (most common, ~85%): RCA gives posterior interventricular artery
• Left dominant (~8%): LCx gives PDA
• Co-dominant (~7%)

• Right atrium (including SA node)
• Right ventricle (most of it)
• Inferior wall of left ventricle
• Posterior 1/3 of interventricular septum
• AV node (usually)

• Inferior MI: ST elevation in II, III, aVF
• SA node dysfunction: sinus bradycardia, sick sinus syndrome
• AV block: 1st, 2nd (Mobitz I/Wenckebach), occasionally 3rd degree
• Right ventricular infarction (look for ST elevation in right-sided leads V3R-V4R)
• Avoid nitrates in RV infarction (RV is preload-dependent)

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15. BRONCHOPULMONARY SEGMENTS OF THE RIGHT LUNG

1. Apical (S1)
2. Posterior (S2)
3. Anterior (S3)

• Each segment has its own segmental bronchus, artery, and vein - can be surgically resected independently (segmentectomy)
• The veins are intersegmental (run between segments, not within them)
• Right eparterial bronchus (upper lobe bronchus): arises above the pulmonary artery - mnemonic "bronchus eparterial" - only on the right
• Aspiration pneumonia in supine patient: right lower lobe (S6 - superior segment) most affected
• Aspiration in erect patient: right lower lobe posterior basal segment (S10)
• Foreign body aspiration: more commonly right lung (right main bronchus is wider, shorter, more vertical)

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16. RECTUM - Clinical

• Upper 1/3: covered on front and sides (intraperitoneal front)
• Middle 1/3: covered on front only
• Lower 1/3: entirely extraperitoneal
• Rectovesical pouch (males) / Rectouterine pouch (Pouch of Douglas) (females): most dependent part of peritoneum - site of pelvic abscess, ascites, peritoneal metastases

• Superior rectal artery (from inferior mesenteric) - main supply
• Middle rectal arteries (from internal iliac)
• Inferior rectal arteries (from internal pudendal)

• Superior rectal vein → inferior mesenteric vein → portal system
• Middle/inferior rectal veins → internal iliac → systemic
• Porto-systemic anastomosis at anorectal junction (pectinate line)

• Above: autonomic innervation; visceral pain; columnar epithelium; lymph to internal iliac nodes; venous drainage to portal system (internal hemorrhoids - not painful)
• Below: somatic innervation (pudendal nerve); sharp pain; squamous epithelium; lymph to inguinal nodes; venous drainage to systemic (external hemorrhoids - painful)

• Carcinoma of rectum: commonest in rectosigmoid junction; DRE most important initial exam; CEA marker
• Hemorrhoids: internal (above pectinate line - painless bleeding); external (below - painful)
• Rectal prolapse: full-thickness vs. mucosal
• Rectal examination: important for prostate assessment, ovarian/uterine pathology through rectovesical/rectouterine pouch

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17. URETER - Clinical

• Descends retroperitoneally on psoas muscle
• Crosses bifurcation of common iliac artery (or external iliac) at pelvic brim
• Passes close to uterine/internal iliac vessels in pelvis
• In females: passes under uterine artery ("water under the bridge") near lateral fornix of vagina
• Enters posterolateral angle of bladder

1. Pelviureteric junction (PUJ) - where renal pelvis becomes ureter
2. Pelvic brim (crossing iliac vessels)
3. Vesicoureteric junction (VUJ) - narrowest point

• Loin-to-groin pain (ureteric colic)
• Radiation to ipsilateral testis/labia (from T10-L1 dermatomes)
• At VUJ: urinary frequency + dysuria (close to bladder trigone)

• Hysterectomy: ureter injured as it passes under uterine artery
• Pelvic surgery: ureter may be ligated, transected, or devascularized
• Abdominoperineal resection: ureter at risk

• Non-contrast CT KUB (gold standard for ureteric calculi)
• IVU/IVP (historically)
• Urinary hydroxyproline levels not useful; urine for hematuria is
• Ultrasound: hydronephrosis/hydroureter

• Duplex ureter: Weigert-Meyer rule: upper pole ureter inserts ectopically (inferiorly/medially); lower pole ureter prone to vesicoureteric reflux
• Retrocaval (circumcaval) ureter: right ureter loops behind inferior vena cava → hydronephrosis

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18. HISTOLOGY - TRACHEA AND OVARY

Trachea - Histology

1. Mucosa:
   • Respiratory epithelium: pseudostratified ciliated columnar epithelium with goblet cells (respiratory epithelium)
   • Cell types: ciliated columnar cells (most numerous), goblet cells (mucus-secreting), basal cells (stem cells), brush cells, small granule cells (neuroendocrine)
   • Lamina propria: loose connective tissue with serous/mucous glands, lymphoid tissue, elastic fibers
2. Submucosa:
   • Dense irregular connective tissue
   • Contains seromucous glands (tracheal glands)
3. Cartilaginous layer:
   • 16-20 C-shaped (U-shaped) hyaline cartilage rings - provide rigidity and keep airway open
   • Open posterior part (trachealis muscle): trachealis smooth muscle bridges the gap posteriorly
   • The posterior membranous wall lies adjacent to the esophagus
4. Adventitia:
   • Fibrous connective tissue blending with surrounding structures

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Ovary - Histology

• Primordial follicles (most numerous): primary oocyte arrested in prophase I of meiosis, surrounded by a single layer of flattened follicular cells
• Primary follicle: oocyte enlarges; follicular cells become cuboidal (unilaminar) then stratified/granulosa cells (multilaminar); zona pellucida begins to form
• Secondary follicle: multiple layers of granulosa cells; theca interna and externa develop from stroma; fluid begins to accumulate (liquor folliculi)
• Graafian (mature) follicle: large fluid-filled antrum (Call-Exner bodies = small eosinophilic droplets between granulosa cells); cumulus oophorus projects into antrum; oocyte resumes meiosis I just before ovulation
• Corpus luteum: after ovulation; granulosa-lutein cells (large, pale, progesterone-secreting) + theca-lutein cells; produces progesterone and estrogen
• Corpus albicans: regressed corpus luteum; white fibrous scar tissue
• Atretic follicles: most follicles (>99%) undergo atresia; glassy membrane (thickened zona pellucida) is characteristic

• Loose connective tissue (hilus)
• Blood vessels, lymphatics, nerves
• Hilus cells (homologous to Leydig cells): may produce androgens; hilar cell tumor → virilization

• Call-Exner bodies in granulosa cell tumor (also normal Graafian follicles)
• Sertoli-Leydig cell tumor (androblastoma): virilization
• Krukenberg tumor: bilateral, mucin-filled signet ring cells from gastric metastasis

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