Digestive System

Mouth and Associated Structures

The mouth, or oral cavity, is the entry point for food and is involved in mechanical and chemical digestion. Several structures contribute to its function:

• Labia: The lips, which form the anterior boundary of the oral cavity.

• Oral cavity: The space within the mouth, bounded by the teeth, tongue, and palate.

• Hard palate: The bony anterior portion of the roof of the mouth, separating the oral and nasal cavities.

• Soft palate: The muscular posterior portion of the palate, which rises during swallowing to close off the nasopharynx.

• Teeth: Structures for mechanical breakdown of food. Key parts include:

  • Dentin: The bulk of the tooth, beneath the enamel.

  • Enamel: The hard, outermost layer protecting the tooth.

  • Root canal: The passageway for nerves and blood vessels within the tooth root.

  • Cementum: Calcified covering of the tooth root.

  • Periodontal ligament: Connective tissue anchoring the tooth to the alveolar bone.

  • Alveolus: The socket in the jawbone where the tooth sits.

  • Gingiva: The gums, which surround the teeth and alveolar bone.

• Uvula: The conical projection from the soft palate, aiding in speech and swallowing.

• Salivary glands: Produce saliva for digestion and lubrication. Types include:

  • Parotid

  • Sublingual

  • Submandibular

• Frenulum: Folds of mucous membrane securing the tongue and lips. Types:

  • Lingual

  • Superior labial

  • Inferior labial

Pharynx and Esophagus

• Oropharynx: The middle part of the pharynx, behind the oral cavity; passageway for food and air.

• Esophagus: Muscular tube transporting food from the pharynx to the stomach.

Stomach

The stomach is a muscular organ for food storage and digestion. Key regions and features include:

• Lesser curvature: The shorter, concave border of the stomach.

• Greater curvature: The longer, convex border.

• Rugae: Folds in the stomach lining that allow expansion.

• Cardia: Region where the esophagus enters the stomach.

• Fundus: Dome-shaped region above the cardia.

• Body: Main central region.

• Pyloric region: Distal region leading to the small intestine.

• Pyloric sphincter: Muscular valve controlling passage of chyme into the duodenum.

Small Intestine

The small intestine is the primary site for digestion and absorption of nutrients. It consists of three regions:

• Duodenum: First segment, receives chyme from the stomach and digestive secretions from the pancreas and liver.

• Jejunum: Middle segment, major site of nutrient absorption.

• Ileum: Final segment, connects to the large intestine at the ileocecal junction.

• Ileocecal junction: The connection between the ileum and cecum of the large intestine.

Large Intestine

The large intestine absorbs water and forms feces. Main structures include:

• Haustra: Pouches in the colon wall caused by the teniae coli.

• Cecum: The first part of the large intestine, receiving material from the ileum.

• Appendix: A small, lymphoid organ attached to the cecum.

• Colon: Divided into ascending, transverse, descending, and sigmoid sections.

• Rectum: Terminal section, stores feces before elimination.

• Anus: The opening for fecal elimination.

Accessory Digestive Organs

• Pancreas:

  • Head, tail, main pancreatic duct, accessory pancreatic duct

• Liver:

  • Lobes: right, left, caudate, quadrate

  • Hepatic ducts (left and right), common hepatic duct, bile duct

  • Falciform ligament: attaches liver to anterior abdominal wall

• Gallbladder:

  • Cystic duct: connects gallbladder to bile duct

Urinary System

Kidney Structure

The kidneys filter blood and produce urine. Key anatomical features include:

• Hilum: Indentation where the ureter, renal artery, and renal vein enter/exit.

• Cortex: The outer region containing renal corpuscles and convoluted tubules.

• Medulla: Inner region containing renal pyramids.

• Renal pyramids: Cone-shaped tissues in the medulla.

• Papillae: Tips of the pyramids where urine drains into minor calyces.

• Calyx (major and minor): Chambers collecting urine from papillae.

• Renal pelvis: Funnel-shaped structure collecting urine from calyces and leading to the ureter.

Urinary Tract

• Ureters: Tubes transporting urine from kidneys to bladder.

• Urinary bladder: Muscular sac for urine storage.

• Trigone: Triangular area in the bladder base, defined by ureteral and urethral openings.

• Internal urethral sphincter: Involuntary muscle controlling urine release from bladder.

• External urethral sphincter: Voluntary muscle controlling urination.

Male Reproductive System

Testes and Associated Structures

• Testes: Male gonads producing sperm and testosterone.

• Tunica vaginalis: Outer serous membrane covering the testes.

• Tunica albuginea: Fibrous capsule surrounding the testes.

• Seminiferous tubules: Site of sperm production.

• Rete testis: Network of tubules transporting sperm from seminiferous tubules.

• Scrotum: Sac holding the testes outside the body for temperature regulation.

• Epididymis: Coiled tube (head, body, tail) for sperm maturation and storage.

• Vas deferens: Duct transporting sperm from epididymis to ejaculatory duct.

• Spermatic cord: Contains vas deferens, blood vessels, nerves, and cremaster muscle.

• Cremaster muscle: Raises and lowers the testes for temperature regulation.

Accessory Glands and Penis

• Seminal vesicle: Produces seminal fluid.

• Ejaculatory duct: Formed by the union of vas deferens and seminal vesicle duct.

• Prostate gland: Secretes fluid that nourishes and protects sperm.

• Prostatic urethra: Portion of urethra passing through the prostate.

• Membranous urethra: Short segment between prostate and penis.

• Bulbourethral gland: Secretes pre-ejaculate fluid for lubrication.

• Penis: Male copulatory organ, containing:

  • Penile (spongy) urethra: Runs through the penis.

  • Corpora cavernosa: Paired erectile bodies.

  • Corpus spongiosum: Surrounds urethra, prevents collapse during erection.

  • Glans: Enlarged tip of the penis.

  • Prepuce: Foreskin covering the glans.

Female Reproductive System

Ovaries and Uterine Tubes

• Ovaries: Female gonads producing ova and hormones.

• Uterine (Fallopian) tubes: Transport ova from ovaries to uterus. Regions include:

  • Isthmus: Narrow medial segment.

  • Ampulla: Wider, central region where fertilization often occurs.

  • Infundibulum: Funnel-shaped distal end.

  • Fimbriae: Finger-like projections that help capture the ovulated egg.

Uterus and Associated Structures

• Uterus: Muscular organ for implantation and development of the embryo. Layers include:

  • Endometrium: Inner mucosal lining, site of implantation.

  • Myometrium: Thick muscular layer.

  • Perimetrium: Outer serous layer.

• Fundus: Dome-shaped superior region.

• Ovarian ligament: Connects ovary to uterus.

• Broad ligament: Supports uterus, fallopian tubes, and ovaries.

• Round ligament: Helps maintain uterine position.

• Cervix: Inferior, narrow portion of uterus; includes internal and external os (openings).

External Genitalia and Mammary Glands

• Vagina: Muscular canal for intercourse and childbirth.

• Labia majora: Outer folds of skin protecting the vulva.

• Labia minora: Inner folds of skin.

• Vestibule: Space between labia minora containing openings of urethra and vagina.

• Clitoris: Erectile tissue, homologous to the penis.

• Urethral orifice: External opening of the urethra.

• Mons pubis: Fatty area overlying the pubic bone.

• Mammary glands: Modified sweat glands for milk production. Structures include:

  • Areola: Pigmented area around the nipple.

  • Alveoli: Milk-producing sacs.

  • Lactiferous ducts: Transport milk to nipple.

  • Lactiferous sinus: Enlarged area of duct for milk storage.

Additional info: Students should be able to identify all listed structures on anatomical images and models, and understand their basic functions and relationships within each organ system.