Comprehensive Human Anatomy Study Guide: Volume 2 - Alimentary, Respiratory, Urinary, and Genital Systems

SPLANCHNOLOGY: GENERAL PRINCIPLES

  • Definition: Splanchnology is the branch of anatomy studying internal organs (splanchna in Greek, viscera in Latin). These are primarily located in the thoracic and abdominal cavities, as well as the head and neck.

  • Organ Systems: Includes alimentary, respiratory, urinary, and genital systems.

  • Functional Classification: Internal organs are referred to as vegetative existence organs (vegetabilis), maintaining homeostasis and metabolism, vs. animal existence organs (soma) responsible for movement and environmental communication.

  • Tubular (Hollow) Organs: Main structural pattern is a tube.

    • Wall Structure: Comprised of four layers:

      • Tunica mucosa: faces the lumen. It consists of the epithelium (stratified squamous, simple columnar/cuboidal, or transitional), lamina propria (loose connective tissue with lymphoid tissue), and muscularis mucosae (smooth muscle for mucosal relief).

      • Tela submucosa: loose connective tissue containing nerves, blood/lymph vessels, ganglia, and glands. It allows mucosa to form folds.

      • Tunica muscularis: typically consists of an inner circular layer (stratum circulare) and an outer longitudinal layer (stratum longitudinale). Smooth muscle provides peristalsis. Striated muscle is found at the beginning/end of tubes for voluntary control.

      • Outer layer: either tunica serosa (peritoneum, pleura, pericardium) with mesothelium for frictionless movement, or tunica adventitia (loose connective tissue) for fixed organs.

  • Parenchymal Organs: (e.g., liver, lungs, kidneys). Consist of:

    • Parenchyma: the specific functional portion of the glandular organ.

    • Stroma: the connective tissue framework/scaffold containing nerves and vessels.

  • Topography: Studied from three positions:

    • Holotopy: Relation of an organ to body surface regions (e.g., epigastric, umbilical).

    • Syntopy: Position relative to neighboring organs, vessels, and nerves.

    • Skeletotopy: Position relative to the skeleton (vertebrae and ribs).

ALIMENTARY SYSTEM: THE ORAL CAVITY AND TEETH

  • Oral Cavity (Cavitas Oris): Divided into the vestibule (vestibulum oris) and oral cavity proper.

  • Palate (Palatum):

    • Hard Palate: formed by bone and covered in mucosa with transverse folds.

    • Soft Palate: mucous-covered muscular structure ending in the uvula. Muscles include $m. tensor veli palatini$ (suppliey by V nerve), $m. levator veli palatini$, $m. uvulae$, $m. palatoglossus$, and $m. palatopharyngeus$ (all supplied by X nerve).

  • Teeth (Dentes):

    • Structure: Crown, neck, and root. Composition: dentine (base), enamel (covering crown), and cement (covering root). The pulp cavity contains vessels and nerves.

    • Anatomy: Gomphosis is the fibrous junction fixing teeth in alveoli via the periodontium.

    • Permanent Formula (32 teeth): $2.1.2.3$ (2 incisors, 1 canine, 2 premolars, 3 molars) per quadrant.

    • Deciduous Formula (20 teeth): $2.0.1.2$ per quadrant. Erupt from 6 months to 2 years.

THE TONGUE AND SALIVARY GLANDS

  • Tongue (Lingua/Glossus):

    • Papillae: Filiform (tactile), fungiform (taste), vallate (V-shaped row, taste), and foliate (margins, taste).

    • Muscles: Intrinsic (alter shape) and extrinsic (genioglossus, hyoglossus, styloglossus - alter position). All supplied by hypoglossal nerve (XII).

    • Innervation: Sensory is complex: Anterior $2/3$ by V (general) and VII (taste via chorda tympani); posterior $1/3$ by IX; root area by X.

  • Major Salivary Glands:

    • Parotid: Largest, produces serous secretion. Ductus parotideus opens opposite the upper 2nd molar.

    • Submandibular: Mixed secretion. Duct opens at the sublingual caruncle.

    • Sublingual: Mostly mucous secretion. Major duct joins submandibular duct.

PHARYNX AND OESOPHAGUS

  • Pharynx: Muscular sac (13-14 cm) connecting nasal/oral cavities to larynx/oesophagus.

    • Parts: Nasopharynx (contains pharyngeal tonsil/adenoids), Oropharynx (crossroads of air and food), Laryngopharynx.

    • Muscles: Constrictors (superior, middle, inferior) and elevators (stylopharyngeus, palatopharyngeus).

    • Lymphoid Ring: Pirogov-Waldeyer’s ring (6 tonsils: 2 palatine, 2 tubal, 1 pharyngeal, 1 lingual).

  • Oesophagus: Tube 26-30 cm long, C6 to Th11 level.

    • Anatomical Constrictions:

      1. Pharyngo-esophageal (C6-C7).

      2. Broncho-aortic (Th4-Th5).

      3. Diaphragmatic (at esophageal hiatus).

STOMACH (GASTER/VENTRICULUS)

  • Parts: Cardia, fundus, body, and pylorus (antrum and canal).

  • Wall Layers: Features oblique muscular fibers (internal layer) unique to the stomach for churning.

  • Topography: 3/4 in left hypochondrium, 1/4 in epigastrium.

  • Pyloric Sphincter: Regulates chyme passage via circular muscle thickening.

INTESTINES

  • Small Intestine:

    • Duodenum: Horseshoe-shaped, 30 cm long. Features major duodenal papilla where bile and pancreatic ducts open.

    • Jejunum and Ileum: Intraperitoneal with mesentery. Mucosa features plicae circulares and villi for absorption. Aggregated lymphoid nodules (Peyer's patches) are found in the ileum.

  • Large Intestine: Characterized by taeniae coli (muscle bands), haustra (sacculations), and appendices omentales (fatty outgrowths).

    • Segments: Caecum (with vermiform appendix), ascending colon, transverse colon, descending colon, sigmoid colon, and rectum.

LIVER, GALLBLADDER, AND PANCREAS

  • Liver (Hepar): Largest gland (1500 g).

    • Surfaces: Diaphragmatic and Visceral (H-shaped grooves containing porta hepatis).

    • Structure: Hexagonal lobules with central veins and hepatic triads (interlobular artery, vein, and bile duct).

  • Gallbladder: Stores/concentrates bile. Cystic duct joins common hepatic duct to form the bile duct (ductus choledochus).

  • Pancreas: Exocrine (digestive juice) and endocrine (Islets of Langerhans - insulin/glucagon).

THE PERITONEUM

  • Structure: Parietal and visceral layers forming the peritoneal cavity.

  • Formations:

    • Lesser Omentum: Hepatogastric and hepatoduodenal ligaments.

    • Greater Omentum: Hangs from greater curvature, 4 layers of fat-laden serosa.

    • Omental Bursa: Space posterior to the stomach communicating with the main cavity via the epiploic foramen (Foramen of Winslow).

RESPIRATORY SYSTEM

  • Nasal Cavity: Respiratory region (ciliary epithelium, cavernous plexuses for warming) and Olfactory region (superior concha area).

  • Larynx: Vocal apparatus. Cartilages: Unpaired (Thyroid, Cricoid, Epiglottis) and Paired (Arytenoid, Corniculate, Cuneiform).

    • Glottis: Consists of vocal folds and the rima glottidis. The posterior crico-arytenoid muscle is the sole abductor (widener) of the glottis.

  • Trachea: C-shaped hyaline cartilages connected by annular ligaments. Membranous posterior wall allows food passage in the oesophagus.

  • Lungs: Right lung has 3 lobes (superior, middle, inferior) and 10 segments. Left lung has 2 lobes and 9-10 segments.

    • Acinus: Structural unit of the lung; everything distal to the terminal bronchiole.

URINARY AND GENITAL SYSTEMS

  • Kidneys (Ren/Nephros): Retroperitoneal at Th12-L2.

    • Nephron: Structural unit (Renal corpuscle + tubules). Filtration occurs in the glomerulus (Malpighian corpuscle).

  • Male Genitalia: Testis (spermatogenesis in seminiferous tubules), Epididymis, Ductus Deferens, Prostate (produces prostatic fluid).

  • Female Genitalia: Ovaries (produce oocytes and hormones), Uterine tubes (site of fertilization), Uterus (Endometrium, Myometrium, Perimetrium), Vagina.

ENDOCRINE GLANDS

  • Pituitary (Hypophysis): Anterior lobe (Adenohypophysis) produces tropic hormones (ACTH, TSH, FSH, LH, STH). Posterior lobe (Neurohypophysis) stores ADH and Oxytocin produced by the hypothalamus.

  • Thyroid: Produces Thyroxin ($T4$), Triiodothyronine ($T3$), and Calcitonin (lowers blood calcium).

  • Suprarenal (Adrenal): Cortex (steroids) and Medulla (epinephrine/norepinephrine).