Vet Tech Midterm Ultimate Study Guide

Digestive System Anatomy and Dietary Adaptations

• Digestion Overview: Mechanical and chemical breakdown of ingested food into absorbable molecules for cellular metabolism, followed by elimination of non-nutritious waste.

• Basic Structures: Oral cavity (lips, teeth, tongue, hard and soft palates, $4$ major pairs of salivary glands), pharynx, esophagus, stomach, small intestine, and large intestine.

• Tooth Anatomy: Consists of the crown, root, enamel, dentin, pulp, cementum, periodontal ligament, and neurovascular supply; deciduous teeth serve as the initial set.

• Dietary Dentition Adaptations:

  • Carnivores: Possess sharp incisors, prominent canines, and specialized carnassial teeth designed for seizing prey and shearing flesh.

  • Herbivores: Possess large, flat premolars and molars, a diastema, and a horny pad adapted for cutting and grinding plant materials.

  • Omnivores: Possess intermediate dentition adapted for processing both plant and animal matter.

Monogastric Digestion and Accessory Organs

• Gastric Processing: Peristalsis transports the swallowed bolus down the esophagus into the simple stomach; parietal cells secrete $HCl$ to produce an acidic environment for enzymatic protein breakdown, converting food into chyme before passage through the pyloric sphincter.

• Small Intestinal Regions and Hormones:

  • Duodenum: Receives pancreatic digestive enzymes and bile; site of critical digestive signaling.

  • Cholecystokinin (CCK): Triggers gallbladder contraction to release bile and stimulates pancreatic enzyme secretion.

  • Secretin: Regulates water homeostasis and balances duodenal fluid balance.

  • Gastric Inhibitory Peptide (GIP): Stimulates insulin release in response to nutrient intake.

  • Jejunum and Ileum: Absorb short peptides, amino acids, sugars, electrolytes, and water across mucosal cells.

• Accessory Organs:

  • Liver: Synthesizes bile to emulsify fats, maintains blood glucose via glycogen storage, converts toxic ammonia into urea, stores iron and vitamins, and metabolizes drugs and toxins.

  • Pancreas: Secretes essential digestive enzymes into the duodenum to complete chyme digestion.

• Large Intestine: Consists of the cecum, colon, and rectum; primarily absorbs water and electrolytes; defecation involves coordinated voluntary and involuntary contractions.

• Equine Hindgut Specialization: Monogastric herbivores featuring an elongated cecum and a four-region colon adapted for plant fiber fermentation.

Ruminant Digestive System

• Symbiotic Fermentation: Relies on symbiotic gut microbes within a specialized four-compartment stomach to break down plant fiber; rumination regurgitates contents for remastication.

• Four Gastric Compartments:

  • Rumen: Large vat occupying the majority of the left abdomen, divided into dorsal and ventral sacs; normally exhibits $2\text{--}3$ mixing contractions per minute.

  • Reticulum: Honeycomb-patterned lining, acting as a single functional fermentation unit with the rumen; site of hardware disease.

  • Omasum: Composed of thin internal tissue leaves that absorb water, nutrients, and electrolytes while blocking coarse particles.

  • Abomasum: The "true stomach" operating via acid and enzymatic secretion to digest unfermented residues.

Respiratory System Structures and Mechanics

• Airway Anatomy:

  • Upper Airway: Mucus-covered epithelium and turbinates in the nose filter inspired air; the soft palate divides the pharynx into nasopharynx and oropharynx; the larynx houses vocal folds and is shielded by the epiglottis during deglutition.

  • Lower Airway: The trachea contains flexible, incomplete C-shaped cartilage rings lined with ciliated epithelium; bifurcates into major bronchi, smaller bronchioles, and terminal alveoli.

• Pulmonary Function:

  • Surfactant: Lipid-protein complex coating alveoli to lower surface tension, prevent collapse, and facilitate lung inflation.

  • Ventilation: Involuntary process directed by the brainstem in response to carbon dioxide fluctuations; inspiration involves downward/caudal excursion of the diaphragm, while expiration involves cranial diaphragm relaxation.

Circulatory System and Cardiac Dynamics

• Blood Fractions:

  • Fluid Fraction: Plasma proteins include albumin, globulins, and fibrinogen; liquid remaining after coagulation is serum.

  • Formed Elements: Red blood cells (erythrocytes, produced via erythropoiesis), white blood cells (leukocytes), and platelets (thrombocytes).

• Vascular Pathway: Blood travels from the heart via arteries $\rightarrow$ arterioles $\rightarrow$ capillaries (nutrient/gas transfer) $\rightarrow$ venules $\rightarrow$ veins back to the heart.

• Cardiac Conduction and ECG Tracing:

  • Conduction Centers: Sinoatrial (SA) node functions as the primary pacemaker; atrioventricular (AV) node provides backup pacing and conducts signals to ventricles.

  • P Wave: Atrial depolarization following SA node firing.

  • QRS Complex: Ventricular contraction (systole).

  • T Wave: Ventricular repolarization (diastole preparation).

• Hemodynamics and Normal Pressures:

  • Heart Sounds: "Lub-dub" valves closing; murmurs indicate turbulent flow or valvular leakage (systolic during contraction, diastolic during relaxation).

  • Normal Blood Pressure: Dogs maintain approximately $\sim 115/65\text{ mmHg}$; cats maintain approximately $\sim 125/88\text{ mmHg}$.

Clinical Veterinary Conditions and Pathology

• Digestive and Metabolic Disorders:

  • Bloat: Ruminal gas entrapment causing severe left-flank distension (frothy or free-gas bloat).

  • Displaced Abomasum: Gas-filled dilation and upward displacement of the fourth stomach, common post-calving.

  • Equine Colic: Severe abdominal discomfort from intestinal spasms, excess gas, or severe impaction.

  • Diarrhea and Vomiting: Rapid fluid loss threatening dehydration and electrolyte depletion; small intestinal diarrhea presents with large fluid volume, while large intestinal diarrhea presents with small, frequent stools with mucus or blood.

• Respiratory Disorders:

  • Tracheal Collapse: Dynamic flattening of tracheal rings producing a dry, "honking" cough (prevalent in Pomeranians, Poodles, Yorkshire Terriers, Chihuahuas, Pugs).

  • Cyanosis: Bluish tissue discoloration indicative of hypoxemia and desaturated hemoglobin.

  • Roaring: Vocal fold hemiplegia during equine exertion.

  • Heaves: Recurrent, noncontagious airway obstruction in horses caused by dust and mold inhalation.

• Circulatory and Hematologic Disorders:

  • Arrhythmias: Deviations from sinus rhythm, including sinus tachycardia, sinus bradycardia, sinus arrhythmia, atrial fibrillation, ventricular fibrillation, and asystole.

  • Anemia: Subnormal red blood cell mass triggered by blood loss, parasitism, toxins, or autoimmune disease.

  • Heart Failure & Shock: Failure to maintain adequate tissue perfusion and oxygen delivery.

• Systemic and Musculoskeletal Conditions:

  • Hypocalcemia (Milk Fever): Acute subnormal blood calcium at parturition.

  • Azotemia and Uremia: Blood elevation of urea nitrogen and creatinine; clinical illness stemming from azotemia is termed uremia.

  • Tying Up & Sweeny: Muscle cramping following rest on full rations in horses (tying up); suprascapular nerve damage causing shoulder muscle atrophy (sweeny).

  • Porcine Stress Syndrome: Defective calcium leakage from the sarcoplasmic reticulum inducing severe involuntary tremors.