Back & Spine
3 concepts
01 Lumbar Puncture & Epidural Anesthesia
Needle enters the subarachnoid space (to sample CSF) or the epidural space (to inject anesthetic).
Level
Inserted between L3/L4 (adults) or L4/L5 (kids) — line through highest points of iliac crests
Cord ends
Spinal cord ends at L2 (conus medullaris) in adults, L3 in children
Dural sac
Ends at S2 — cauda equina + filum terminale below
Layers
Skin → supraspinous lig → interspinous lig → ligamentum flavum → epidural space → dura → arachnoid → CSF
Spinal nerves: 8 cervical · 12 thoracic · 5 lumbar · 5 sacral · 1 coccygeal
02 Herniated Intervertebral Disc
Nucleus pulposus herniates posterolaterally through the anulus fibrosus and compresses a nerve root.
Common sites
Lumbar L4/L5 or L5/S1; cervical C5/C6 or C6/C7
Rule
Herniation compresses the nerve root one number below (L4/L5 herniation → compresses L5 root)
Symptoms
Back pain radiating down the lower limb; decreased reflexes on the affected side; pain after lifting
Ligaments
Posterior longitudinal ligament is narrow → herniations go postero-lateral
03 Abnormal Curvatures of the Spine
Three deformities: Kyphosis (thoracic), Lordosis (lumbar), Scoliosis (lateral).
Kyphosis
Exaggerated thoracic curvature — elderly, from osteoporosis / vertebral compression fractures
Lordosis
Exaggerated lumbar curvature — pregnancy, spondylolisthesis, potbelly
Scoliosis
Complex lateral deviation/torsion — poliomyelitis, leg-length discrepancy, hip disease
Upper Limb
9 concepts
04 Upper Limb Fractures
Classic fracture–nerve pairings and the wrist fractures tested on Step 1.
Humerus nerves
Surgical neck → axillary n; midshaft → radial n; supracondylar → median n / brachial a; medial epicondyle → ulnar n
Colles fracture
Distal radius from FOOSH → fragment displaced dorsally (“dinner-fork deformity”)
Smith fracture
Fall on dorsal flexed wrist → fragment displaced anteriorly
Scaphoid
FOOSH → pain in anatomical snuffbox; risk of avascular necrosis (proximal fragment); may not show on X-ray for 2–3 wks
Boxer fracture
Neck of 5th metacarpal (unskilled fighter); 2nd/3rd in trained boxers
05 Rotator Cuff Muscles (SITS)
S-I-T-S form a musculotendinous cuff reinforcing the shoulder on all sides except inferiorly (site of most dislocations).
Supraspinatus
Initiates abduction (0–15°) — suprascapular n
Infraspinatus
Lateral rotation — suprascapular n
Teres minor
Lateral rotation — axillary n
Subscapularis
Medial rotation — upper/lower subscapular n
06 Abduction of the Upper Limb
Abduction happens in three stages, each driven by a different muscle/nerve.
0–15°
Supraspinatus (suprascapular n) initiates
15–110°
Deltoid (axillary n) to horizontal
110–180°
Scapular rotation by trapezius (accessory n CN XI) + serratus anterior (long thoracic n)
07 The Three Elbows
Student’s (olecranon bursitis), Tennis (lateral epicondylitis), Golfer’s (medial epicondylitis).
Student elbow
Subcutaneous olecranon bursitis — repeated pressure/friction over olecranon bursa
Tennis elbow
Lateral epicondylitis — common extensor tendon; pain over lateral epicondyle, worse opening a door/lifting a glass
Golfer elbow
Medial epicondylitis — common flexor tendon at medial epicondyle
08 Arterial Anastomoses Around the Scapula
Blockage of the subclavian/axillary artery can be bypassed by scapular anastomoses between the thyrocervical and subscapular arteries.
Thyrocervical branches
Transverse cervical a · Suprascapular a
Subscapular branches
Subscapular a · Circumflex scapular a
Key
Suprascapular a (above transverse scapular lig) anastomoses with circumflex scapular a from the triangular space
09 Cubital Fossa
Anterior elbow; contents lateral→medial: biceps tendon, brachial artery, median nerve.
Deep contents
Biceps brachii tendon → Brachial artery → Median nerve (T-A-N)
Superficial
Cephalic v (lateral), median cubital v (joins cephalic + basilic), basilic v (medial)
Venipuncture
Usually the median cubital vein — overlies bicipital aponeurosis, so deep structures protected
10 Carpal Tunnel Syndrome
Compression of the median nerve in the carpal tunnel (fluid retention, infection, lunate dislocation).
Nerve
Median nerve — most sensitive/affected structure in the tunnel
Signs
Pins & needles / anesthesia of lateral 3.5 digits; ape-hand deformity (loss of opposition, thenar wasting)
Spared
Palmar sensation preserved — palmar cutaneous branch passes superficial to the tunnel
Ulnar (Guyon) tunnel: compression between pisiform & hook of hamate → medial 1.5-finger hypoesthesia + partial claw hand
11 Test of the PIP & DIP Joints
Isolating the finger flexors identifies which tendon/nerve is intact.
PIP
FDS (Flexor Digitorum Superficialis) — median n
DIP
FDP (Flexor Digitorum Profundus) — ulnar & median n
MCP
Lumbricals flex the metacarpophalangeal joints
12 Lesions of Upper-Limb Nerves
Brachial plexus & peripheral nerve palsies: know the roots and the hand posture.
Erb-Duchenne (upper)
C5–C6 / superior trunk — “waiter’s tip”: adducted shoulder, medially rotated arm, extended elbow (birth/fall)
Klumpke (lower)
C8–T1 / inferior trunk — claw hand + ape hand; may include Horner syndrome (sudden upward pull)
Peripheral
Median = ape hand/benediction · Ulnar = claw hand · Radial = wrist drop
Musculocutaneous
Lateral cord lesion → weak elbow flexion (biceps/brachialis) + supination; anesthesia over lateral forearm
Lower Limb
8 concepts
13 Cardiac Catheterization (Femoral Artery)
The femoral artery is the classic access for cardiac catheterization.
Left heart
Cannulate femoral a → external iliac → common iliac → aorta → left ventricle / coronary arteries
Right heart
Peripheral vein (femoral v) → IVC → RA → RV → pulmonary trunk/arteries for pressures & samples
14 Gluteal Region & Femoral Neck Fractures
Femoral neck fracture in elderly women; nerve injuries of the gluteal region.
Femoral neck #
Elderly women (osteoporosis) → shortened + laterally rotated limb; disrupts blood supply → hip replacement
AVN femoral head
Transcervical fracture disrupts medial circumflex femoral a (retinacular aa) → avascular necrosis
Sciatic n
Foot drop, flail foot; injured by improper gluteal injection or posterior hip dislocation — inject in upper outer quadrant
Gluteal nerves
Superior gluteal n → Trendelenburg sign (contralateral pelvic drop); inferior gluteal n → weak hip extension (climbing stairs)
Obturator n
Difficulty adducting thigh + sensory loss over medial thigh; waddling gait
15 Avulsion Fractures & Hamstrings
Avulsion fractures occur where muscles attach — e.g. the ischial tuberosities (hamstring origin).
Hamstrings
Biceps femoris (long head), Semitendinosus, Semimembranosus
Action
Extension of hip + flexion of knee
Nerve
Tibial n (short head of biceps femoris = common fibular n)
16 Structures Under the Inguinal Ligament & Femoral Hernia
Lateral→medial under the inguinal ligament, and the femoral hernia that follows.
Lateral → medial
Iliopsoas · Femoral Nerve · Femoral Artery · Femoral Vein · Femoral canal (deep inguinal nodes)
Femoral triangle
Superior = inguinal lig; medial = adductor longus; lateral = sartorius
Femoral hernia
Passes below inguinal lig through femoral canal → swelling inferolateral to pubic tubercle; more common in females; risk of strangulation
17 Knee Joint Injuries
The unhappy triad, collateral & cruciate ligaments, and knee bursae.
Unhappy triad
Lateral blow (football tackle) → TCL (MCL) + medial meniscus + ACL
Collaterals
TCL/MCL attaches to medial meniscus (limits abduction); FCL/LCL does NOT attach to lateral meniscus
Cruciates
ACL rupture → anterior drawer sign; PCL rupture → posterior drawer sign
Bursae
Prepatellar bursitis (“housemaid’s knee”); suprapatellar bursa — site for intra-articular injection
Knee-jerk
Patellar reflex tests L2–L4 (femoral n)
18 Ankle Joint Injuries
Sprains are the most common ankle injury; Pott fracture is a fracture-dislocation.
Sprain
Inversion injury → lateral ligament (anterior talofibular) — weaker than the medial deltoid lig
Pott fracture
Forced eversion → avulses medial malleolus (deltoid lig) then fibula fractures higher up
Ankle-jerk
Achilles reflex tests S1–S2 (tibial n)
19 Injuries of the Leg & Foot
Fibular neck fracture, Achilles rupture, and plantar fasciitis.
Fibular neck #
Injures common fibular (peroneal) n → paralysis of anterior/lateral compartments → foot drop + dorsum sensory loss
Achilles rupture
Avulsion of calcaneal tendon disables triceps surae (gastrocnemius + soleus + plantaris) → cannot plantarflex
Plantar fasciitis
MC hindfoot problem in runners → heel pain, point tenderness at proximal plantar aponeurosis (calcaneal spur)
20 Injury of the Tibial Nerve
Tibial nerve injury in the popliteal fossa → loss of plantar flexion and sole sensation.
Popliteal fossa
Loss of plantar flexion (gastrocnemius/soleus) + weak inversion → calcaneovalgus; can’t stand on toes
Sole
Medial plantar n — abductor hallucis, FDB, FHB, 1st lumbrical + medial 3.5 digits; Lateral plantar n — all other intrinsics + lateral 1.5 digits
Note
Common fibular n does NOT pass through the popliteal fossa (wraps around fibular neck)
Thorax
11 concepts
21 Breast: Carcinoma, Lymphatics & Infection
Breast cancer, its lymphatic spread, mastectomy risks, and mastitis.
Carcinoma
Adenocarcinoma of lactiferous duct epithelium; tethers suspensory (Cooper) ligaments → skin dimpling
Lymphatics
>75% (lateral quadrants) → axillary nodes; medial quadrants → parasternal nodes / opposite breast
Mastectomy risks
Long thoracic n (winged scapula, serratus anterior) & intercostobrachial n (medial arm sensory loss)
Mastitis
Infection during breastfeeding — bacteria enter a milk duct via cracked nipple
22 Thoracic Wall & Diaphragm
Intercostal neurovascular bundle, the phrenic nerve, and diaphragm paralysis.
Intercostal VAN
In the costal groove, superior→inferior: Vein, Artery, Nerve; run between internal & innermost intercostals
Thoracocentesis
Insert above the rib (avoid VAN) — 9th–10th intercostal space
Phrenic n
C3, C4, C5 keeps the diaphragm alive; runs anterior to lung root; sensory to pericardium/mediastinal & diaphragmatic pleura
Paralysis
Phrenic n injury → paradoxical movement (dome pushed up on inspiration); detected radiologically
Openings
IVC T8 · Esophagus T10 · Aorta T12
23 Cardiac Hypertrophy
Left atrial enlargement (mitral valve failure) can compress the esophagus.
Mechanism
Mitral regurgitation → LA pressure/dilation → hypertrophy
Sign
Enlarged LA compresses the esophagus → dysphagia; filling defect on barium swallow
Cardiac shadow
Right border = SVC + RA; Left border = aortic arch, pulmonary trunk, left auricle, LV
24 Auscultation of Heart Valves
A murmur is heard downstream from its valve.
Aortic
2nd right intercostal space, parasternal
Pulmonic
2nd left intercostal space, parasternal
Tricuspid
Left lower sternal border (4th/5th ICS)
Mitral
Cardiac apex — 5th left ICS, midclavicular line
25 Conducting System of the Heart
SA node → AV node → bundle of His → bundle branches → Purkinje fibers.
SA node
Pacemaker — upper sulcus terminalis near SVC opening
AV node
Lower interatrial septum near coronary sinus (triangle of Koch)
His / branches
Membranous interventricular septum → right (moderator band) & left bundle branches → Purkinje fibers
26 Blood Supply of the Heart
Coronary anatomy and the blood supply of the conduction system.
RCA
Right atrium/ventricle; SA node (60%) & AV node branches; posterior interventricular a → inferior wall + posterior 1/3 septum
LCA
LAD (“widow-maker”, MC site of MI) → anterior 2/3 septum, apex; circumflex → LA/LV
Conduction supply
SA node & AV node = RCA; AV bundle + moderator band = LCA
27 Congenital Cardiac Defects
Left-to-right (acyanotic) shunts and coarctation of the aorta.
ASD
Failure of foramen ovale closure → left-to-right shunt, acyanotic; usually ostium secundum
VSD
Most common congenital defect; membranous septum → RV hypertrophy, left-to-right shunt
PDA
Failure of ductus arteriosus closure (PGE + low O₂ keep it open); rubella; ligation endangers left recurrent laryngeal n → hoarseness
Coarctation
Narrowing distal to left subclavian → upper-limb HTN, rib notching (intercostal collaterals)
28 Aspiration & Bronchopulmonary Segments
Aspirated bodies favor the right bronchus; know the segment counts.
Aspiration
Foreign bodies enter the right primary bronchus (wider, more vertical) → middle/lower lobe; supine → posterior segment of RLL
Right lung
10 segments (upper 3, middle 2, lower 5)
Left lung
9 segments (lingula replaces middle lobe; cardiac notch)
29 Lung Diseases
Pneumonia and the complications of bronchogenic carcinoma.
Pneumonia
Inflammation from infection/chemical injury; CXR opacity + mediastinal lymph node enlargement
Bronchogenic ca
Persistent cough/hemoptysis; early spread to bronchomediastinal nodes
Pancoast tumor
Apex tumor → thoracic outlet syndrome (C8–T1) + Horner syndrome (miosis, ptosis, anhidrosis)
Other
SVC syndrome (facial swelling, cyanosis) · dysphagia · hoarseness (recurrent laryngeal n) · diaphragm paralysis (phrenic n)
30 Open Pneumothorax & Pleura
Air enters the pleural cavity → lung collapse; pleural reflections.
Open pneumothorax
Stab wound pierces parietal pleura → pleural cavity open to air → lung collapse + mediastinal shift
Cervical pleura
May be injured by improper subclavian venipuncture
Costodiaphragmatic recess
Deepest part of pleural cavity — where pleural effusion collects; midclavicular ribs 6–8, midaxillary 8–10, paravertebral 10–12
Pleural innervation
Parietal pleura = somatic (intercostal + phrenic n, pain-sensitive); visceral = autonomic (insensitive)
31 Mediastinum, Thoracic Duct & Esophagus
Superior mediastinum contents, thoracic duct drainage, and esophageal constrictions.
Superior mediastinum
Aortic arch & branches, brachiocephalic veins, trachea/esophagus — at T4/T5 (angle of Louis)
Thoracic duct
Drains 3/4 of the body (all but right upper quadrant) → junction of left jugular/subclavian veins
Esophageal constrictions
C6 (pharynx, 15 cm) · T4/5 (aortic arch + left bronchus, ~25 cm) · T10 (diaphragm, ~40 cm) — sites of foreign-body lodging & carcinoma
Abdomen
22 concepts
32 Anterior Abdominal Wall
Nerve & arterial supply of the anterior abdominal wall.
Nerves
7 nerves: lower 5 intercostals + subcostal + L1 (iliohypogastric & ilioinguinal)
Deep arteries
Superior epigastric (internal thoracic) + inferior epigastric (external iliac) — in the neurovascular plane between internal oblique & transversus
Superficial
Superficial epigastric & superficial circumflex iliac (from femoral a)
Portal-caval anastomosis of paraumbilical veins → caput medusae
33 Herniations
The hernial sac has 3 parts; indirect vs direct inguinal hernias.
Parts
Hernial sac (peritoneal diverticulum), contents (usually small bowel), coverings (abdominal wall layers)
Indirect
Most common; congenital; lateral to inferior epigastric vessels; through deep ring → into scrotum; 20× more in males
Direct
Medial to inferior epigastric vessels (Hesselbach triangle); old men, weak wall; does NOT enter scrotum
First layer
Transversalis fascia is the first structure crossed by any abdominal hernia
34 Peritoneal Structures
Lesser omentum, the epiploic foramen, and the rectouterine pouch.
Lesser omentum
Hepatogastric + hepatoduodenal ligaments; free edge holds the portal triad (bile duct, portal vein, proper hepatic a)
Epiploic (Winslow) foramen
Anterior = portal triad; posterior = IVC; superior = caudate lobe; inferior = 1st duodenum — site of Pringle maneuver
Pouch of Douglas
Rectouterine pouch — lowest peritoneal point in females; site of pelvic abscess; drained by culdocentesis (posterior fornix)
35 Foregut / Midgut / Hindgut (Smart Table)
Artery, autonomic supply, and referred pain of the three gut divisions.
Foregut
Artery celiac (T12); PSNS vagus; SNS greater splanchnic T5–T9; referred to epigastrium
Midgut
Artery SMA (L1); PSNS vagus; SNS lesser splanchnic T10–T11; referred to umbilicus
Hindgut
Artery IMA (L3); PSNS pelvic splanchnic S2–S4; SNS lumbar splanchnic L1–L2; referred to hypogastrium
Retroperitoneal (SAD PUCKER): Suprarenal, Aorta/IVC, Duodenum 2–3, Pancreas, Ureters, Colon (asc/desc), Kidneys, Esophagus, Rectum
36 Posterior Gastric Ulcer
A posterior gastric ulcer erodes into the omental bursa and splenic artery.
Erosion
Erodes posterior stomach wall → omental (lesser) bursa → pancreas → referred pain to the back
Bleeding
Splenic artery erosion is common due to its proximity to the posterior wall
37 Congenital Diaphragmatic Hernia
Abdominal viscera herniate through a posterolateral diaphragmatic defect.
Defect
Foramen of Bochdalek — posterolateral, usually left (liver closes the right first)
Cause
Improper fusion of pleuroperitoneal membranes
Danger
High mortality from pulmonary hypoplasia
38 Sliding Hiatal Hernia
Cardia of the stomach slides into the thorax through the esophageal hiatus.
Mechanism
Past middle age; cardia herniates through the esophageal hiatus (often shortened esophagus)
Consequence
Can damage vagal trunks → hyposecretion of gastric juice
39 Meckel Diverticulum
Persistent vitellointestinal (omphalomesenteric) duct — the classic “rule of 2s.”
Origin
Congenital remnant of the vitelline duct; true diverticulum
Rule of 2s
~2% of people, ~2 feet from ileocecal junction, ~2 inches long, presents ~age 2, 2:1 male; SMA supply
Ectopic tissue
Gastric/pancreatic tissue → ulceration, bleeding; mimics appendicitis
40 Features of the Large Intestine
Distinguishing features and the intra/retroperitoneal course of the colon.
Features
Appendices epiploicae, haustra (sacculations), teniae coli (converge at appendix base)
Positions
Ascending & descending colon = retroperitoneal; transverse & sigmoid = intraperitoneal (mesocolon)
Flexures
Right (hepatic) & left (splenic) flexures
41 Appendicitis & McBurney Point
Pain migrates from the umbilicus to McBurney point.
First pain
Visceral, referred to the umbilicus (T10) — distension/spasm
Second pain
Once parietal peritoneum is involved, pain localizes to McBurney point (2/3 from umbilicus to ASIS)
42 Volvulus
A mobile loop rotates around its mesentery → avascular necrosis.
Sites
Sigmoid colon, cecum, jejunum/ileum — extreme mobility
Result
Rotation around mesentery → obstructed blood supply → avascular necrosis
43 Hirschsprung Disease
Congenital absence of ganglion cells → functional obstruction.
Cause
Aganglionic segment — neural crest cells fail to reach colon; absent postganglionic parasympathetic neurons
Association
Down syndrome; males > females
Newborn
Failure to pass meconium in 1–2 days, bilious vomiting, distension → megacolon; Rx = resect aganglionic segment
44 Abdominal Aorta & Mesenteric Ischemia
Aortic branch levels, the AAA, and mesenteric ischemia.
Levels
Celiac T12 · SMA L1 · Renal L2 · IMA L3 · bifurcation L4
AAA
Localized dilatation, usually below the renal arteries (L4); rupture mortality ~90%; repair with graft
Mesenteric ischemia
Atherosclerosis of SMA → jejunum/ileum most compromised; age >60, smoking, high cholesterol
45 Biliary System & Gallstones
Bile ducts, Calot triangle, and where gallstones impact.
Ducts
Cystic duct + common hepatic duct → common bile duct → joins main pancreatic duct at ampulla (sphincter of Oddi) → 2nd duodenum
Calot triangle
Cystic duct, common hepatic duct, inferior liver — locate cystic artery
Gallstones
Impact at the hepatopancreatic ampulla → obstructive jaundice; cystic-duct stone = biliary colic without jaundice; fundus stone can erode into transverse colon
46 Nerve Supply of Liver & Gallbladder
Autonomic and referred innervation of the liver/gallbladder.
Sensory (referred)
Right phrenic n (C3–C5) → pain radiates to the right shoulder
Parasympathetic
Vagus (CN X) via celiac plexus
Sympathetic
Greater splanchnic (T5–T9) via celiac plexus
47 Portal Hypertension & Portocaval Shunts
Portal-systemic anastomoses that dilate in portal hypertension.
Esophageal
Left gastric (portal) ↔ azygos (systemic) → esophageal varices → hematemesis
Umbilical
Paraumbilical ↔ epigastric veins → caput medusae
Rectal
Superior rectal (portal) ↔ middle/inferior rectal (systemic) → internal hemorrhoids
Surgical shunts
Splenorenal (extrahepatic) & portacaval (portal vein → IVC) divert blood to systemic system
48 Pancreas
Parts of the pancreas, cancer of the head, and annular pancreas.
Head/uncinate
In the C-shaped duodenum; traversed by CBD; uncinate crossed by superior mesenteric vessels
Neck/body/tail
Neck overlies formation of the portal vein; tail enters splenorenal lig to the spleen hilum (only intraperitoneal part)
Head cancer
Compresses bile duct → obstructive jaundice (no fever); pain to T5–T9 dorsal roots
Annular pancreas
Ventral + dorsal buds ring the duodenum → obstruction + polyhydramnios; bilious vomiting
49 Spleen: Rupture
Splenic rupture from left lower rib fractures/blunt trauma.
Location
LUQ, deep to left ribs 9–11 (follows rib 10)
Rupture
Left rib fracture or blunt trauma; blood under diaphragm irritates phrenic n → left shoulder pain
Management
Cannot be sutured → splenectomy
50 Kidney: Position & Relations
Kidney dimensions, relations, and the renal fascia.
Position
T12 → L3; right kidney lower (liver); hilum at L1 (vein–artery–ureter, front→back)
Anterior relations
Right: suprarenal, 2nd duodenum, liver, colic flexure, small bowel. Left: suprarenal, stomach, pancreas, spleen, colon
Gerota fascia
Renal fascia encloses kidney + suprarenal; must be incised in surgery
Perinephric abscess
Spreads along psoas major; upward spread irritates diaphragm/phrenic n → shoulder pain
51 Nephrolithiasis
Renal calculi types, ureter constrictions, and staghorn stones.
Stones
Majority calcium oxalate, then calcium phosphate
Ureter constrictions
Pelviureteric junction (L1) · pelvic brim (sacroiliac) · entry into bladder (ischial spine)
Staghorn
Struvite (Mg-ammonium-phosphate) at high urine pH — recurrent UTI (Proteus)
52 Suprarenal Glands
Endocrine cortex + catecholamine medulla and their 3 arteries.
Cortex
Aldosterone, cortisol, sex steroids
Medulla
Chromaffin cells → epinephrine/norepinephrine; tumor (pheochromocytoma) → episodic tachycardia, sweating, HTN
Arteries
Superior (phrenic a), middle (aorta), inferior (renal a)
53 Varicocele
Enlargement of the pampiniform plexus — a “bag of worms.”
Feature
Enlarged pampiniform plexus → low sperm count; usually left side; disappears when supine
Left drainage
Left testicular v → left renal v (right → IVC directly); nutcracker syndrome
Warning
Sudden right varicocele that doesn’t disappear → retroperitoneal malignancy obstructing the testicular vein
Pelvis & Perineum
18 concepts
54 Hydrocele
Fluid in the tunica vaginalis — transilluminates.
Cause
Patent processus vaginalis / tunica vaginalis → fluid collection
Sign
Transillumination positive (reddish glow); does NOT disappear when supine (vs varicocele)
Compare
Torsion twists the testis → ischemia → must be corrected quickly
55 Hemorrhoids
The pectinate line divides painless internal from painful external hemorrhoids.
Above pectinate
Superior rectal vein → portal system; visceral innervation → painless internal hemorrhoids
Below pectinate
Inferior rectal vein → IVC; somatic (inferior rectal n) → painful external hemorrhoids
Association
Internal hemorrhoids in chronic alcoholics (cirrhosis + portal HTN)
56 Perineal Pouches
Deep vs superficial perineal pouch contents and urine extravasation.
Deep pouch
Between perineal membrane & pelvic diaphragm: sphincter urethrae, deep transverse perineal m, bulbourethral (Cowper) glands (males)
Superficial pouch
Ischiocavernosus, bulbospongiosus, superficial transverse perineal m (+ perineal body)
Urine leak
Ruptured spongy urethra at bulb of penis → urine into superficial perineal pouch → up over pubis into abdominal wall
57 Ischiorectal Abscess
Infection in the ischiorectal fossa — a surgical emergency.
Origin
Spread through external anal sphincter into the ischiorectal fossa
Management
Surgical emergency → immediate wide cruciate incision (drain) to avoid fistula
Avoid
Lateral wall — contains pudendal (Alcock) canal with pudendal n & internal pudendal a
58 Cystocele
Herniation of the bladder from pelvic-floor damage in childbirth.
Cause
Loss of bladder support from pelvic-floor damage during childbirth
Result
Bladder protrudes onto the anterior vaginal wall → stress incontinence; extreme cases → vaginal prolapse
59 Paracentesis of the Urinary Bladder
Suprapubic aspiration of a full bladder avoids the peritoneum.
Technique
Needle inserted just above the pubic symphysis into a full bladder
Path
Skin → fascia → linea alba → transversalis fascia → extraperitoneal tissue → bladder — does not cross peritoneum
60 Prostate Tumors
Prostate cancer (posterior lobe) vs BPH (middle lobe), and prostatectomy risks.
Cancer
Posterior lobe; found on digital rectal exam; metastasizes to vertebrae/brain via vertebral (Batson) venous plexus
BPH
Middle lobe → urethral obstruction, nocturia, dysuria, urgency
Prostatectomy
Damage to cavernous nerves → impotence/incontinence; pelvic splanchnic n at risk
61 Male Urethra
Three parts of the male urethra and its two sphincters.
Prostatic (1st)
Widest & most dilatable; receives ejaculatory ducts + prostatic ductules
Membranous (2nd)
Shortest, narrowest, least dilatable; through urogenital diaphragm; surrounded by external sphincter
Spongy (3rd)
Longest (~15 cm); through bulb + corpus spongiosum to external meatus; bulbourethral ducts open here
Sphincters
Internal = smooth muscle, sympathetic; External = skeletal, pudendal n
62 Ejaculatory Duct
Short duct formed by the ductus deferens + seminal vesicle duct.
Formation
Union of ductus deferens + duct of seminal vesicle
Course
~2 cm; carries seminal fluid to the prostatic urethra
63 Pudendal Nerve (S2–S4)
Principal somatic nerve of the perineum; site of pudendal block.
Course
Against the ischial spine, through lesser sciatic foramen, into pudendal (Alcock) canal
Branches
Inferior rectal n (external anal sphincter) · perineal n · dorsal n of penis/clitoris
Block
For episiotomy — pierce vaginal wall near ischial spine; uterine (visceral) pain is unaffected
64 Nerve Supply of Pelvic Viscera
Autonomic innervation of pelvic viscera and the micturition reflex.
Parasympathetic
Pelvic splanchnic n (S2–S4) → intramural plexus
Sympathetic
Sacral splanchnic n (T12–L2) → inferior hypogastric plexus
Micturition
PSNS + pudendal to pee (detrusor contracts, sphincters relax); SNS to stop (inhibits detrusor, closes internal sphincter)
65 Erection & Ejaculation
“Point (parasympathetic) and Shoot (sympathetic).”
Erection
Parasympathetic (S2–S4) pelvic splanchnic n → dilate arteries; ischiocavernosus/bulbospongiosus press the root
Emission/Ejaculation
Sympathetic (L1–L2) → smooth muscle of ducts/seminal vesicles/prostate + internal sphincter closes (prevents retrograde)
Afferent
Dorsal n of penis/clitoris (pudendal, S2–S4)
66 Cryptorchism
Undescended testis — fails to reach the scrotum.
Definition
Testis fails to descend (normally within 3 months after birth); found in inguinal canal/abdomen
Risks
Malignant transformation & arrested spermatogenesis → sterility if bilateral
67 Torsion of the Spermatic Cord
Twisting of the cord → testicular avascular necrosis.
Cord contents
Ductus deferens, testicular artery (direct branch of aorta), pampiniform plexus
Torsion
Acute pain + swelling; twists testicular artery → avascular necrosis; needs urgent detorsion + orchiopexy
68 Lymphatic Drainage of the Viscera
Genital lymphatics: scrotum/vulva vs testis/ovary.
Testis / ovary
→ lumbar (para-aortic) nodes (follow gonadal vessels)
Scrotum / vulva
→ superficial inguinal nodes
Anal canal
Above pectinate line → internal iliac; below → superficial inguinal
Glans
Glans penis/clitoris → deep inguinal nodes
69 Uterine Arteries & Hysterectomy
Uterine artery supply and the ureter at risk in hysterectomy.
Supply
Uterine artery (internal iliac) crosses the pelvic floor in the cardinal ligament
Ureter
“Water (ureter) under the bridge (uterine a)” — ureter at greatest risk during hysterectomy
Ovarian supply
Ovarian a (direct from aorta) — preserved in partial hysterectomy
70 Parts of the Uterine Tube
Uterine (Fallopian) tube segments and the site of fertilization.
Segments
Uterine part → isthmus (narrowest) → ampulla → infundibulum (fimbriae)
Fertilization
Usually in the ampulla — site of ectopic pregnancy
Imaging
Hysterosalpingography detects tubal obstruction / bicornuate uterus
71 Branches of the Internal Iliac Artery
Anterior vs posterior division branches of the internal iliac artery.
Anterior division
Obturator · umbilical · inferior gluteal · internal pudendal · inferior vesical (vaginal) · middle rectal · uterine
Posterior division
Iliolumbar · lateral sacral · superior gluteal
Head & Neck
26 concepts
72 Fracture of the Anterior Cranial Fossa
Cribriform plate fracture → anosmia, raccoon eyes, CSF rhinorrhea.
Sign
Fracture of the cribriform plate (ethmoid) → anosmia, periorbital bruising (raccoon eyes), CSF rhinorrhea
73 Cranial Malformations
Premature suture closure → characteristic skull shapes (FGFR2).
Scaphocephaly
Premature sagittal suture closure → long, narrow, wedge skull
Oxycephaly
Premature coronal suture closure → tower skull
Plagiocephaly
One-sided coronal/lambdoid closure → twisted, asymmetric skull
74 Epidural Hematoma
Pterion fracture tears the middle meningeal artery → biconvex bleed.
Cause
Skull fracture near the pterion → torn middle meningeal a (foramen spinosum)
Course
Rapid unconsciousness/death — strips dura; biconvex (lens) shape on CT
CN III
Uncal herniation → CN III compression (blown pupil, ptosis, eye down-and-out)
76 Infection of the Cavernous Sinus
The “dangerous triangle” of the face drains to the cavernous sinus.
Danger triangle
Middle third of face; facial v → ophthalmic v → cavernous sinus → thrombophlebitis → meningitis/thrombosis
Passing through
Internal carotid a & CN VI (abducens) → internal squint first
Lateral wall
CN III, IV, V₁, V₂
77 Pituitary Tumors & Transsphenoidal Surgery
Pituitary tumors compress the optic chiasm; surgery goes through the sphenoid.
Extension
Superior extension → pressure on the optic chiasm → bitemporal hemianopia; endocrine disturbance
Surgery
Transsphenoidal — through nose, nasal cavity, sphenoid sinus (best exposure, lowest risk)
Hormones
Anterior: ACTH, FSH, LH, TSH, prolactin, GH; Posterior: ADH, oxytocin (made in hypothalamus)
78 Trigeminal Nerve (CN V)
Sensory to the face via three divisions; motor to mastication (V3).
Divisions
V₁ forehead/sinuses/nose · V₂ cheeks/upper mouth · V₃ chin, lower mouth, anterior 2/3 tongue (general), muscles of mastication
Exception
Skin over the angle of the mandible → great auricular n (C2–C3), not CN V
Note
Taste anterior 2/3 tongue = CN VII (chorda tympani), not V
79 Bell Palsy
Idiopathic unilateral facial (CN VII) paralysis.
Cause
Idiopathic; CN VII lesion (may follow parotid tumor/inflammation — stylomastoid foramen)
Signs
Cannot close eye (dry eye) or lips on affected side; cannot whistle/blow; facial distortion
80 Epistaxis
Most nosebleeds are from the anterior septum (Kiesselbach plexus).
Site
Anterior nasal septum — Kiesselbach (Little) area
Vessels
Sphenopalatine + anterior ethmoidal + greater palatine + superior labial arteries converge
81 Sinusitis (Sphenoid & Ethmoid)
Sphenoid & ethmoid sinus infections can erode into orbit/cranium.
Sphenoiditis
May erode to cavernous sinus, pituitary, optic nerves/chiasm; important during pituitary surgery
Ethmoiditis
Erodes the medial orbital wall → orbital cellulitis; affects medial rectus, superior oblique, nasociliary n
83 Cheeks
Buccinator and the parotid duct opening.
Buccinator
Principal muscle of the cheek
Parotid duct
Pierces buccinator, opens opposite the 2nd upper molar
84 Movements at the TMJ
Muscles of mastication (all V3) and mandibular deviation.
Elevation
Temporalis, masseter, medial pterygoid
Protrusion/Depression
Lateral pterygoid — the only opener; opens jaw + protrusion
Deviation
Mandibular n damage → jaw deviates toward the lesioned side (weak lateral pterygoid)
85 Innervation of the Tongue
Sensory, taste, and motor supply of the tongue.
Anterior 2/3
General = lingual n (V₃); taste = chorda tympani (VII)
Posterior 1/3
General + taste = glossopharyngeal (IX)
Motor
Hypoglossal (XII) — lesion → tongue deviates toward the lesioned side
86 Gag Reflex
Afferent CN IX, efferent CN X.
Afferent
Glossopharyngeal (CN IX)
Efferent
Vagus (CN X)
Lesion
CN IX injury → negative gag reflex
87 Palatine Tonsils
Blood supply, drainage, and innervation of the palatine tonsils.
Blood supply
Tonsillar branch of the facial artery
Drainage
Jugulodigastric node — most frequently enlarged node in the body
Nerves
CN IX & CN X; tonsillectomy risks the facial a & internal carotid a
88 Muscles of the Soft Palate
Soft-palate muscles (all CN X via pharyngeal branch except tensor).
Muscles
Tensor veli palatini (V₃), levator veli palatini, palatoglossus, palatopharyngeus, musculus uvulae
Function
Elevate soft palate during swallowing to prevent nasopharyngeal reflux
Lesion
Vagus lesion → uvula deviates away from the lesion
89 Lymph Drainage from the Face
Facial lymph nodes and their territories.
Preauricular (parotid)
Anterolateral scalp + eyelids
Submandibular
Air sinuses, nose, cheek, upper lip, lateral lower lip
Submental
Chin, tip of tongue, central lower lip
90 Blow-Out Fracture
Blunt trauma fractures the orbital floor into the maxillary sinus.
Mechanism
Blunt trauma to orbital contents → orbital floor blows out into the maxillary sinus
Damage
Inferior rectus muscle, infraorbital n (V₂ numbness), infraorbital a (hemorrhage)
91 Muscles of the Orbit
Extraocular muscles, their actions, and innervation.
Innervation
LR₆ SO₄ AR₃ — Lateral rectus = CN VI; superior oblique = CN IV; all others = CN III
Superior oblique
Depresses + abducts a medially rotated eye (looking down/in)
Inferior oblique
Elevates + abducts the eye
92 Strabismus (CN III / IV / VI Palsy)
Extraocular nerve palsies and eye position.
CN III palsy
“Down and out” eye + ptosis + fixed dilated pupil (external squint)
CN IV palsy
Superior oblique paralysis → eye slightly up; diplopia going down stairs
CN VI palsy
Lateral rectus paralysis → internal squint (eye adducted)
93 Horner Syndrome
Interruption of the ascending sympathetic chain.
Cause
Neck injury, Pancoast tumor, or thyroid carcinoma interrupting preganglionic sympathetics (T1 → superior cervical ganglion)
Signs
Ptosis · Anhidrosis · Miosis (+ vasodilation/warmth)
94 Otitis Media & Tympanic Perforation
Middle-ear inflammation and eardrum perforation.
Otitis media
Diminished hearing (ossicle pressure), altered taste (chorda tympani); spread → mastoiditis, meningitis, sigmoid sinus thrombosis
Perforation
From otitis media, foreign body, diving, trauma; chorda tympani damage → loss of taste anterior 2/3 tongue; large tears need repair
95 Thyroid & Parathyroid Glands
Thyroid/parathyroid relations, nerves at risk, and the thyroglossal cyst.
Thyroid
Largest endocrine gland → T3/T4 (metabolism) + calcitonin (↓ Ca²⁺); parathyroid PTH (↑ Ca²⁺)
Nerves at risk
Recurrent laryngeal n (with inferior thyroid a) → hoarseness; external laryngeal n (with superior thyroid a) → cricothyroid
Median cervical cyst
Painless midline mass below hyoid, moves on swallowing; remnant of the thyroglossal duct; Rx = excision
96 Larynx
Laryngeal folds, muscles, and cricothyrotomy.
Folds
Vestibular (false) & vocal (true) folds; rima glottidis = narrowest point (limits tube size)
Muscles
Posterior cricoarytenoid = only abductor of the vocal folds (recurrent laryngeal n); lesion → hoarseness
Cricothyrotomy
Emergency airway — incision through cricothyroid membrane (between cricoid & thyroid cartilage)
98 Retropharyngeal Space
Interval between the pharynx and prevertebral fascia — a route to the mediastinum.
Boundaries
Between buccopharyngeal fascia (pharynx) & prevertebral fascia
Danger
Passage for infection from pharynx → posterior mediastinum (mediastinitis ~90% mortality)
99 Axillary Sheath
Prevertebral fascia extension enclosing the axillary neurovascular bundle.
Origin
Derived from prevertebral fascia
Contents
Encloses the subclavian artery + brachial plexus in the interscalene space; extends into the axilla
100 Posterior Triangle of the Neck
Boundaries and contents of the posterior triangle.
Boundaries
Clavicle, sternocleidomastoid, trapezius
Contents
External jugular v, occipital a, accessory n (CN XI), brachial plexus trunks, cervical plexus, phrenic n, superficial cervical nodes
CN XI
Supplies SCM & trapezius — injury → weak shoulder shrug / head turn