Integumentary System, Eye and Ear Anatomy, Heart and Great Vessels, Arteries/Veins/Lymphatics, and Pulmonary Anatomy, condensed to the highest-yield facts.
| Topic | One-glance facts |
|---|---|
| Epidermal layers | Deep → superficial: stratum basale (germinativum, mitotic stem cells + melanocytes) → spinosum (desmosomes, Langerhans cells) → granulosum (keratohyalin granules) → lucidum (thick/glabrous skin only — palms, soles) → corneum (dead, keratinized, flakes off). |
| Skin color pigments | Melanin (melanocytes in stratum basale, UV protection) + carotene (diet-derived yellow-orange, stratum corneum/subcutaneous fat) + hemoglobin (dermal vessels, pink/red hue) combine to determine skin tone. |
| Dermis: papillary vs. reticular | Papillary layer = superficial, loose areolar connective tissue, forms dermal papillae, rich in capillary loops and Meissner corpuscles. Reticular layer = deeper, thicker, dense irregular connective tissue; gives skin its structural strength/elasticity. |
| Subcutaneous tissue & fascia | Hypodermis (superficial fascia) = areolar + adipose, insulation/cushioning, Pacinian corpuscles at its deep margin. Retinacula cutis anchor dermis to deep fascia, which wraps muscles into fascial planes/compartments. |
| Sweat & other accessory structures | Eccrine glands = widespread, primary thermoregulatory sweat glands. Apocrine glands = confined to axillae/groin, active at puberty. Sebaceous glands (holocrine) secrete sebum into hair follicles. Arrector pili muscle on hair follicle produces goosebumps. |
| Burn classification by depth | 1st-degree = epidermis only (e.g., sunburn, no blistering). 2nd-degree = extends into dermis (painful, blistering). 3rd-degree = full-thickness skin destruction, often painless centrally from nerve destruction; frequently needs grafting. |
| Stretch marks vs. tension lines | Striae = tearing of dermal collagen/elastic fibers when skin stretches faster than the reticular layer can remodel. Langer's lines = predominant collagen fiber orientation in reticular dermis; incisions parallel to them scar less. |
| Topic | One-glance facts |
|---|---|
| Eye's three tunics | Fibrous tunic = sclera (opaque, posterior) + cornea (transparent, refracts light). Vascular tunic (uvea) = choroid (nourishes retina) + ciliary body (aqueous humor, accommodation) + iris (pupil diameter). Neural tunic = retina. |
| Eye chambers/humors | Anterior cavity (aqueous humor) splits into anterior chamber (cornea–iris) and posterior chamber (iris–lens). Posterior/vitreous cavity (behind lens) holds gel-like vitreous humor, maintaining eyeball shape. |
| Extrinsic eye muscle innervation | "LR6 SO4 3" rule: lateral rectus by CN VI, superior oblique by CN IV, remaining four extrinsic muscles (superior/inferior/medial rectus, inferior oblique) by CN III. |
| Retina: rods, cones, optic disc | Rods = dim-light/peripheral vision, no color. Cones = 3 subtypes, color vision + acuity, concentrated at cone-only fovea centralis (sharpest vision). Optic disc = ganglion axons exit as optic nerve, no photoreceptors → blind spot. |
| Visual pathway | Retina ganglion cells → optic nerve (CN II) → optic chiasm (nasal/medial fibers cross, temporal/lateral stay uncrossed) → optic tract → lateral geniculate nucleus (thalamus) → optic radiations → primary visual cortex (occipital lobe). |
| Ear regions & ossicles | External ear (auricle + meatus) → tympanic membrane → middle ear (air-filled, ossicles malleus–incus–stapes, stapes footplate at oval window; Eustachian tube to nasopharynx) → inner ear (bony labyrinth/perilymph housing membranous labyrinth/endolymph). |
| Cochlea & vestibular complex | Scala vestibuli + scala tympani (perilymph) sandwich scala media/cochlear duct (endolymph, organ of Corti). Utricle/saccule detect linear acceleration/tilt via otoliths; semicircular canals/ducts (3 planes) detect angular acceleration via ampullae. |
| Topic | One-glance facts |
|---|---|
| Pericardium layers | Fibrous pericardium (tough outer sac, anchors heart) + serous pericardium (parietal layer lining fibrous sac, visceral layer/epicardium on heart surface) with pericardial cavity/fluid between them. |
| Heart wall layers | Epicardium (= visceral pericardium) → myocardium (contractile cardiac muscle, reinforced by fibrous skeleton anchoring valves and electrically insulating atria from ventricles) → endocardium (lines chambers/valves). |
| Chambers & valves | RA (from venae cavae + coronary sinus) and LA (from pulmonary veins) receive; RV (→pulmonary trunk) and LV (most muscular, →aorta) pump. AV valves (tricuspid/mitral) held by chordae tendineae + papillary muscles; semilunar valves (pulmonary/aortic) need no chordae — cusps fill and snap shut. |
| Conduction system | SA node (right atrium, intrinsic pacemaker) → spreads across atria → AV node (delays signal) → AV bundle (bundle of His) → right/left bundle branches → Purkinje fibers. AV valve closure = S1; semilunar valve closure = S2. |
| Coronary vessels | Left coronary artery → anterior interventricular (LAD, anterior septum + LV) + circumflex. Right coronary artery → posterior interventricular + marginal branches, typically supplies SA/AV nodes. Cardiac veins drain via coronary sinus into RA. |
| Aorta: 4 parts | Ascending aorta (coronary arteries only) → aortic arch (brachiocephalic trunk, left common carotid, left subclavian) → thoracic (descending) aorta → abdominal aorta (celiac trunk, superior mesenteric, inferior mesenteric, renal/gonadal) → paired common iliac arteries. |
| Topic | One-glance facts |
|---|---|
| Vessel wall layers | Tunica intima (endothelium + thin connective tissue) → tunica media (smooth muscle + elastic fibers, thickest layer in arteries, drives vasoconstriction/dilation) → tunica externa/adventitia (anchoring connective tissue). |
| Artery types & capillaries | Elastic (conducting) arteries = large, near heart, recoil between beats. Muscular (distributing) arteries = most named arteries, regulate regional flow. Arterioles = smallest, primary resistance vessels. Capillaries = single endothelial layer, only site of exchange. |
| Veins & venous return | Veins have thinner tunica media and larger lumens than arteries, with one-way venous valves (especially in limbs). Venous return is assisted by the skeletal muscle pump and the respiratory pump. |
| Major venous convergence | Brachiocephalic veins (head/neck/upper limb drainage) join to form the SVC; lower-body drainage converges as the IVC. The azygos system (azygos + hemiazygos + accessory hemiazygos) is a collateral pathway into the SVC if the IVC is obstructed. |
| Blood composition | Plasma ≈ 55% of volume (water, electrolytes, plasma proteins: albumin, globulins, clotting factors). Formed elements ≈ 45%: RBCs (erythrocytes, most numerous, carry O2 via hemoglobin), WBCs (leukocytes), platelets (clotting). |
| Lymphatic drainage pathway | Blind-ended lymphatic capillaries (highly permeable) → valved lymphatic vessels → filter through lymph nodes → lymphatic trunks. Thoracic duct drains below-diaphragm + left-body-above into left IJ/subclavian junction; right lymphatic duct drains right upper body into the right-sided junction. |
| Key lymphoid organs | Spleen filters blood and mounts immune responses to blood-borne pathogens. Thymus is the site of T-lymphocyte maturation. Tonsils guard the pharyngeal entrance to the airway/digestive tract. |
| Topic | One-glance facts |
|---|---|
| Pharynx regions vs. larynx | Nasopharynx (adenoid, auditory tube opening) → oropharynx (palatine + lingual tonsils, shared air/food) → laryngopharynx (shared, continues to larynx/esophagus). Larynx itself is a dedicated, cartilage-built airway carrying only air. |
| Laryngeal cartilage framework | Unpaired: thyroid cartilage (laryngeal prominence), cricoid cartilage (only complete cartilage ring in airway), epiglottis (elastic, folds over inlet during swallowing, vallecula anterior to it). Paired: arytenoid cartilages (anchor/rotate vocal folds), plus corniculate and cuneiform. |
| Vocal folds & glottis | True vocal folds vibrate to produce sound as air passes between them; vestibular (false) vocal folds sit above and are protective, not phonatory. Glottis = vocal folds + rima glottidis (the space between them). |
| Trachea structure | ≈15–20 C-shaped hyaline cartilage rings, open posteriorly where trachealis muscle spans the gap (lets esophagus bulge during swallowing); lined by ciliated pseudostratified respiratory epithelium continuing the mucociliary escalator. |
| Lung lobes & bronchial branching | Right lung: 3 lobes (oblique + horizontal fissures). Left lung: 2 lobes (single oblique fissure, cardiac notch, lingula). Primary (main) bronchi → secondary/lobar bronchi (3 right, 2 left) → tertiary/segmental bronchi, each supplying a bronchopulmonary segment. |
| Conducting vs. respiratory zone | Conducting zone (trachea → terminal bronchioles) moves air, no gas exchange. Respiratory zone (respiratory bronchioles → alveolar ducts → alveoli) is where gas exchange occurs, via thin type I pneumocytes and surfactant-secreting type II pneumocytes. |
| Diaphragm hiatuses | Caval opening at T8 (inferior vena cava); esophageal hiatus at T10 (esophagus + vagus nerves); aortic hiatus at T12 (aorta, thoracic duct, azygos vein) — mnemonic: vertebral level matches each structure's letter count (vena cava=8, esophagus=10, aortic=12). |