Anatomy: High-Yield Summary Language of Anatomy Anatomical position: upright, facing forward, arms at the sides with palms forward, feet together. Every descr…

Anatomy: High-Yield Summary

Language of Anatomy

  • Anatomical position: upright, facing forward, arms at the sides with palms forward, feet together. Every description assumes it, whatever the patient's real posture.
  • Planes: median (midline, right/left halves), sagittal (parallel to median), frontal/coronal (front/back), transverse/axial (upper/lower).
  • Proximal/distal refer to the origin of a limb or tube, not to the head. Ipsilateral = same side; contralateral = opposite side.
  • Latin roots: foramen (hole), fossa (shallow depression), incisura (notch), fissura (cleft), tuberositas (rough raised area), condylus (rounded articular end), crista (crest).
  • Always start a name with its type: os, m., a., v., n., lig., art. (plural mm., aa., vv., nn., ligg., artt.).
  • Bone shapes: long, short, flat, irregular, sesamoid (patella). Long bone = epiphysis, metaphysis (growth plate), diaphysis, periosteum.
  • Joints: fibrous (sutura, gomphosis, syndesmosis), cartilaginous (synchondrosis = hyaline, symphysis = fibrocartilage), synovial (hinge, pivot, condyloid, saddle, ball and socket, plane).
  • CNS vs PNS: nucleus/tractus (CNS) vs ganglion/nervus (PNS).

Basic Embryology

  • Fertilization in the ampulla of the uterine tube: capacitation → acrosome reaction → fusion (meiosis II completes) → cortical reaction blocks polyspermy.
  • Week 1: cleavage → morula (inner cell mass = embryoblast, outer = trophoblast) → blastocyst → implantation around day 6.
  • Week 2 ("twos"): cytotrophoblast + syncytiotrophoblast (makes hCG); epiblast + hypoblast; amniotic cavity + yolk sac.
  • Week 3 (gastrulation): epiblast cells pass through the primitive streak to form endoderm, mesoderm and ectoderm. The notochord induces the neural plate (SHH) and persists as the nucleus pulposus.
  • Neural tube closes by day 25 (cranial) and day 28 (caudal); failure causes anencephaly or spina bifida. Folic acid before conception prevents most cases.
  • Somites: sclerotome (vertebrae, ribs), dermatome (dermis), myotome (muscle). Intermediate mesoderm → kidneys and gonads. Lateral plate → body wall, limb skeleton, heart, gut wall.
  • Gut arteries: foregut – coeliac trunk; midgut – superior mesenteric; hindgut – inferior mesenteric.
  • Left–right: FGF8 → Nodal/Lefty2 → PITX2 on the left; Lefty1 is the midline barrier.

Thoracic Cage and Vertebral Column

  • Sternal angle (angle of Louis): rib II joins here, level of the T4/T5 disc. Count ribs from it.
  • Ribs: true I–VII, false VIII–X, floating XI–XII. Typical III–IX; atypical I, II, X, XI, XII. Rib I has the scalene tubercle (subclavian vein in front, artery and lower trunk behind).
  • Intercostal space takes the number of the rib above. Apex beat: 5th left intercostal space, midclavicular line.
  • Neurovascular bundle (vein, artery, nerve) runs in the costal groove under each rib, so needles go over the rib below.
  • Intercostals: external (inspiration), internal (forced expiration), innermost. Posterior intercostal arteries from the aorta (3–11); anterior from the internal thoracic artery (1–6).
  • Vertebrae: cervical = foramen transversarium; thoracic = costal facets; lumbar = neither, large kidney-shaped body. C1 has no body; C2 has the dens; C7 is the vertebra prominens.
  • Curves: primary thoracic and sacral kyphoses; secondary cervical and lumbar lordoses.
  • Disc: anulus fibrosus + nucleus pulposus. Herniation goes posterolaterally, usually at L4–L5 and L5–S1.
  • Ligaments: anterior longitudinal limits extension; ligamenta flava join laminae. Erector spinae = iliocostalis, longissimus, spinalis (dorsal rami).

Cranium

  • Neurocranium (8): frontal, ethmoid, sphenoid, occipital; paired temporal and parietal. Viscerocranium (14): mandible, vomer; paired maxilla, zygomatic, nasal, lacrimal, palatine, inferior concha.
  • Fontanelles: anterior (rhomboid, closes 18–24 months), posterior (triangular, 2–3 months). Bulging = raised intracranial pressure; sunken = dehydration.
  • Pterion (frontal, parietal, sphenoid, temporal) overlies the middle meningeal artery: fracture → epidural haematoma. Bregma and lambda mark the old fontanelles.
  • Foramina: cribriform plate (I), optic canal (II), superior orbital fissure (III, IV, V1, VI), rotundum (V2), ovale (V3), spinosum (middle meningeal artery), internal acoustic meatus (VII, VIII), jugular foramen (IX, X, XI), hypoglossal canal (XII), stylomastoid foramen (VII to the face).
  • Cranial fossae: anterior (frontal lobes), middle (temporal lobes, pituitary), posterior (cerebellum, brainstem).

Face and Neck

  • Scalp (SCALP): skin, dense connective tissue, aponeurosis, loose connective tissue (danger space), pericranium.
  • "V feels, VII moves": trigeminal is sensory to the face (V3 also motor to mastication); facial nerve (temporal, zygomatic, buccal, marginal mandibular, cervical) moves the face.
  • Mastication (V3): temporalis, masseter and medial pterygoid close the jaw; lateral pterygoid opens it.
  • External carotid branches: superior thyroid, ascending pharyngeal, lingual, facial, occipital, posterior auricular, maxillary, superficial temporal.
  • Danger triangle: facial vein → ophthalmic veins → cavernous sinus.
  • Carotid sheath: carotid arteries, internal jugular vein, vagus nerve. Hyoid at C3, the only bone with no bony joint.
  • Anterior triangle (midline, SCM, mandible): submandibular, submental, carotid, muscular triangles. Posterior triangle (SCM, trapezius, clavicle): accessory nerve, brachial plexus trunks, subclavian artery.
  • Thyroid (C5–T1): superior and inferior thyroid arteries; recurrent laryngeal nerve at risk (hoarseness). PTH raises calcium, calcitonin lowers it.
  • All head and neck lymph → deep cervical nodes. Left supraclavicular (Virchow's) node may signal abdominal cancer.
  • Bell's palsy (LMN VII) affects the whole side including the forehead; a stroke (UMN) spares the forehead.

Upper Limb

  • Clavicle is the most commonly fractured bone (middle/lateral third junction).
  • Nerves at risk on the humerus: axillary (surgical neck), radial (radial groove), ulnar (behind medial epicondyle).
  • Carpals: scaphoid, lunate, triquetrum, pisiform / trapezium, trapezoid, capitate, hamate. Snuffbox tenderness = scaphoid fracture (risk of avascular necrosis).
  • Rotator cuff (SITS): supraspinatus (initiates abduction), infraspinatus, teres minor, subscapularis (lesser tubercle). Teres major is not part of it.
  • Nerve territories: musculocutaneous (arm flexors), radial (all extensors), median (forearm flexors except FCU and medial FDP, plus LOAF hand muscles), ulnar (most intrinsic hand muscles), axillary (deltoid, teres minor).
  • Brachial plexus C5–T1: roots, trunks, divisions, cords (lateral, medial, posterior), branches. Long thoracic (C5–C7) supplies serratus anterior.
  • Spaces: quadrangular (axillary nerve, posterior circumflex humeral artery); triangular interval (radial nerve, profunda brachii).
  • Cubital fossa (lateral → medial): radial nerve, biceps tendon, brachial artery, median nerve. Carpal tunnel: FDS, FDP, FPL tendons and the median nerve.
  • Deformities: wrist drop (radial), claw hand (ulnar), hand of benediction (median), winged scapula (long thoracic), carpal tunnel syndrome (median at the wrist).
  • Veins: cephalic (thumb side), basilic (little-finger side), median cubital (venepuncture). Breast lymph → anterior axillary nodes.

Lower Limb

  • Hip bone = ilium + ischium + pubis, fused at the acetabulum. Femoral neck angle about 125°.
  • Talus has no muscle attachments. Chopart's joint = talonavicular + calcaneocuboid; Lisfranc's = tarsometatarsal.
  • Ligaments: iliofemoral is the strongest in the body. ACL stops anterior tibial slide (Lachman); PCL stops posterior slide (dashboard injury). Inversion sprain tears the anterior talofibular ligament first.
  • Gluteal: maximus extends the hip (inferior gluteal nerve); medius and minimus abduct it (superior gluteal nerve; weakness → Trendelenburg sign). Inject into the upper outer quadrant.
  • Thigh nerves: femoral (quadriceps, sartorius), obturator (adductors; pectineus is femoral), sciatic (hamstrings).
  • Leg compartments: anterior (deep fibular, dorsiflexion), lateral (superficial fibular, eversion), posterior (tibial, plantar flexion; triceps surae → Achilles tendon).
  • Greater sciatic foramen: above piriformis the superior gluteal nerve and vessels; below it the sciatic nerve and the rest.
  • Femoral triangle (NAVEL): nerve, artery, vein, empty canal, lymphatics. Femoral ring bounded medially by the lacunar ligament; femoral hernias strangulate easily.
  • Adductor canal: femoral vessels and saphenous nerve under sartorius. Popliteal fossa: nerves superficial, artery deepest.
  • Behind the medial malleolus: Tom, Dick And Very Nervous Harry.
  • Pulses: femoral (midinguinal point), popliteal, posterior tibial (behind medial malleolus), dorsalis pedis (lateral to EHL).
  • Great saphenous vein passes in front of the medial malleolus to the femoral vein; small saphenous behind the lateral malleolus to the popliteal vein.
  • Clinical: foot drop (common fibular nerve at the fibular neck), Achilles rupture (positive Thompson test), avascular necrosis of the femoral head (medial circumflex femoral artery), compartment syndrome (pain out of proportion, early fasciotomy).