Essential Human Anatomy: Systems, Structures, and Functions

Posted on May 26, 2026 in Biology

History of Anatomy

Ancient Greece & Rome

  • Aristotle: Coined “anatome”; dissected animals and named the aorta.
  • Herophilus: Known as the “Father of Anatomy”; performed the first human dissections in Alexandria.
  • Galen: Dissected monkeys and pigs; his teachings dominated medicine for 1,300 years.

Renaissance Anatomy

  • Leonardo da Vinci: Dissected over 30 bodies and created 750+ detailed anatomical drawings.
  • Andreas Vesalius: The “Founder of Descriptive Anatomy”; published De fabrica (1543), correcting over 200 of Galen’s errors through human dissection.

Spleen Anatomy

Topography & Peritoneal Relation

  • Location: Left hypochondriac region, deep to ribs 9–11.
  • Syntopy: Contacts the diaphragm, stomach, left kidney, and colon.
  • Peritoneum: Intraperitoneal; fixed by the gastrosplenic and splenorenal ligaments.

Structure & Abnormalities

  • Structure: Fibrous capsule containing white pulp (immune function) and red pulp (blood filtration).
  • Abnormalities: Splenomegaly (enlargement), splenunculi (accessory spleens), and wandering spleen.

Functions & Neurovascular Supply

  • Functions: Filters old RBCs, immune defense, blood storage, and fetal hematopoiesis.
  • Arteries: Splenic artery (from celiac trunk).
  • Veins: Splenic vein (drains into the portal vein).
  • Nerves: Splenic plexus (derived from celiac plexus and vagus nerve).

Trigeminal Nerve (CN V)

Structure & Topography

  • Type: Mixed nerve (large sensory root, small motor root).
  • Origin: Emerges from the ventrolateral pons.
  • Ganglion: Trigeminal (Gasserian) ganglion located in Meckel’s cave.

Branches & Supply Areas

  • Ophthalmic (V1): Sensory only; passes through the superior orbital fissure. Supplies the forehead, upper eyelid, and cornea.
  • Maxillary (V2): Sensory only; passes through the foramen rotundum. Supplies the cheek, upper teeth, nasal mucosa, and upper lip.
  • Mandibular (V3): Mixed; passes through the foramen ovale.
  • V3 Sensory: Lower jaw, lower teeth, and anterior 2/3 of the tongue.
  • V3 Motor: Muscles of mastication, mylohyoid, anterior digastric, and tensor tympani.

General Anatomy of Muscles

Structure of Muscle as an Organ

  • Skeletal Muscle: An organ composed of muscle tissue, connective tissue, and neurovascular bundles.
  • Connective Layers: Epimysium (outer), perimysium (surrounds fascicles), and endomysium (surrounds individual fibers).
  • Tendons: Dense regular connective tissue anchoring muscle to bone periosteum.

Classification & Function

  • Classification: By shape (long, short, flat), structure (parallel, fusiform, pennate), location, and function (agonists, antagonists, synergists).
  • Anatomical vs. Physiological Diameter: Physiological cross-section is larger in pennate muscles, indicating greater force production.
  • Types of Levers: First class (equilibrium), second class (strength), and third class (speed).

Endocrine Glands

Classification by Embryonic Origin

  • Branchiogenic: Endoderm-derived (e.g., thyroid, parathyroid).
  • Neurogenic: Ectoderm-derived (e.g., hypophysis, pineal gland).
  • Adrenal: Split origin (cortex: mesoderm; medulla: ectoderm).
  • Coelomic: Mesoderm-derived (e.g., gonadal interstitial cells).

General Characteristics

  • Absence of excretory ducts, abundant vascularization, production of potent hormones, and systemic regulation via the hypothalamo-hypophyseal system.

Facial Nerve (CN VII)

Structure & Topography

  • Origin: Cerebellopontine angle (posterior pons).
  • Course: Internal acoustic meatus → facial canal → stylomastoid foramen → parotid gland.
  • Terminal Branches: Temporal, zygomatic, buccal, marginal mandibular, and cervical.
  • Supply: Muscles of facial expression, secretomotor to glands, and taste to the anterior 2/3 of the tongue.

N.I. Pirogov and P.F. Lesgaft

  • N.I. Pirogov: Pioneer of topographical anatomy; developed “Ice Anatomy” (sectioning frozen cadavers) and sculptural anatomy for surgical precision.
  • P.F. Lesgaft: Pioneer of functional anatomy; established the principle that form and function are interdependent and adapt to mechanical stress.

Larynx: Cavity and Wall Structure

  • Cavity Sections: Vestibule, middle cavity (interventricular), and infraglottic cavity.
  • Wall Structure: Respiratory epithelium (ciliated pseudostratified) except for true vocal cords (stratified squamous).
  • Skeleton: Unpaired (thyroid, cricoid, epiglottic) and paired (arytenoid, corniculate, cuneiform) cartilages.

Lower Limb Innervation

  • Lumbar Plexus: Femoral nerve (anterior thigh) and obturator nerve (medial thigh).
  • Sacral Plexus: Superior/inferior gluteal nerves and the sciatic nerve.
  • Sciatic Branches: Tibial nerve (posterior leg) and common fibular nerve (lateral/anterior leg).

Femur Muscles & Adductor Canal

  • Medial Compartment: Adductors (pectineus, longus, gracilis, brevis, magnus); supplied by the obturator nerve.
  • Posterior Compartment: Hamstrings (biceps femoris, semitendinosus, semimembranosus); supplied by the tibial nerve.
  • Adductor Canal: Contains the femoral artery, femoral vein, and saphenous nerve.

Mammary Gland

  • Topography: Superficial fascia over ribs 2–6.
  • Structure: 15–20 lobes supported by Cooper’s ligaments.
  • Supply: Internal/lateral thoracic and intercostal arteries; T4–T6 intercostal nerves.

Upper Limb Nerve Supply

  • Musculocutaneous: Anterior arm muscles.
  • Median: Forearm flexors and thenar muscles.
  • Ulnar: Intrinsic hand muscles and some forearm flexors.
  • Radial: Extensors of the arm, forearm, and hand.
  • Axillary: Deltoid and teres minor.

Shoulder Anatomy

  • Muscles: Deltoid, supraspinatus, infraspinatus, teres minor, teres major, and subscapularis.
  • Canalis Humeromuscularis: Quadrangular space containing the axillary nerve and posterior circumflex humeral artery.

Peritoneum & Bursae

  • Lesser Omentum: Connects stomach/duodenum to the liver; contains the portal triad.
  • Omental Bursa: Lesser sac behind the stomach; communicates with the greater sac via the epiploic foramen.

Accessory & Hypoglossal Nerves

  • Accessory (CN XI): Motor to sternocleidomastoid and trapezius.
  • Hypoglossal (CN XII): Motor to all intrinsic and extrinsic tongue muscles (except palatoglossus).

Ribs, Sternum & Middle Ear

  • Thorax: 12 pairs of ribs (true, false, floating); sternum (manubrium, body, xiphoid).
  • Middle Ear: Tympanic cavity, ossicles (malleus, incus, stapes), and auditory tube.

Cranium, Vas Deferens & Olfactory Nerve

  • Cranium: Neurocranium and viscerocranium; ossification via intramembranous and endochondral processes.
  • Vas Deferens: Muscular tube within the spermatic cord.
  • Olfactory (CN I): Sensory fibers passing through the cribriform plate to the olfactory bulb.

Bone, Small Intestine & Spinal Cord

  • Bone: Compact/spongy structure; osteon as the basic unit; intramembranous/endochondral development.
  • Small Intestine: Jejunum (wider) and ileum (narrower with Peyer’s patches).
  • Spinal Cord: Meninges (dura, arachnoid, pia); blood supply via anterior/posterior spinal arteries.

Back Muscles, Pharynx & Cerebellum

  • Back: Superficial (trapezius, latissimus dorsi) and deep (erector spinae) muscles.
  • Pharynx: Naso-, oro-, and laryngopharynx; Waldeyer’s tonsillar ring.
  • Cerebellum: Hemispheres, vermis, and three peduncles (superior, middle, inferior) for motor coordination.