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Animal Anatomy and Physiology - Video Lecture Notes Review

Foundations of Anatomy and Physiology

  • Anatomy: science of the structure of the body and the relation of its parts.
  • Physiology: science of how the body functions.
  • In veterinary technology, understanding anatomy and physiology is essential for procedures such as radiography positioning, surgical prep, catheter placement, and disease management.

Cell Structure and Physiology

  • Cells are the basic unit of life; they are either prokaryotes or eukaryotes.

  • Prokaryote = “Before Nucleus”: lacks a true membrane-bound nucleus and organelles; all bacteria are prokaryotes.

  • Eukaryote = “True Nucleus”: has a membrane-bound nucleus and numerous membrane-bound organelles; all multicellular organisms are composed of eukaryotic cells.

  • Composition of eukaryotic cells: three major parts — cell membrane, cytoplasm, and nucleus.

  • Cell membrane (plasma membrane)

    • Separates cell from external environment.
    • Structure: double phospholipid layer with interspersed proteins (fluid-mosaic model); contains carbohydrate chains and cholesterol.
    • Semipermeable: allows selective movement of substances.
    • Surface modifications: cilia (hairlike; surface movement), flagellum (long; cellular movement), microvilli (increase surface area; especially in absorptive cells).

  • Cytoplasm

    • Encompasses everything inside the cell except the nucleus.
    • Contains organelles with specialized functions.

  • Organelles

    • Ribosomes: float freely or attach to rough endoplasmic reticulum (RER); composed of protein and rRNA; site of protein synthesis.
    • Mitochondria: powerhouses of the cell; contain mitochondrial DNA and protein; double membrane with cristae; cristae increase surface area for ATP production via cellular respiration (Krebs/citric acid cycle).
    • Endoplasmic reticulum (ER):
    • Rough ER (RER): flattened channels with ribosomes; transports proteins.
    • Smooth ER (SER): no ribosomes; synthesizes cholesterol, steroid hormones, lipids; detoxifies drugs; breaks down glycogen; transports fats. Liver, intestinal, and testicular interstitial cells have abundant SER.
    • Golgi complex: stack of membranes that receive, modify, package, and export substances from ER; also produces lysosomes.
    • Lysosomes: digestive enzymes; digest intracellular bacteria and nonfunctional organelles; autolysis occurs if lysosomal enzymes are released; abundant in phagocytic cells.
    • Peroxisomes: contain oxidases and catalases; detoxify substances; convert free radicals into hydrogen peroxide and then water; abundant in liver and kidney.
    • Cytoskeleton: microtubules, microfilaments, intermediate filaments; provides form, structure, support; anchors organelles; enables movement.
    • Centrioles: form microtubules into a hollow tube; organize the mitotic spindle; form bases of cilia and flagella.
    • Nucleus: control center; contains DNA; governs heredity and protein synthesis; chromatin in nondividing cells; chromosomes during division; double semipermeable nuclear membrane; nucleoli produce ribosomal units.

Movement In and Out of Cells

  • Key definitions:

    • Solute: substance that can be dissolved.
    • Solvent: the dissolving medium.
    • Solution: solute dissolved in solvent; uniform mixture.
    • Intracellular: inside a cell.
    • Extracellular: outside a cell.
    • Intercellular (interstitial): between cells.

  • Passive processes (no energy required)

    • Diffusion: movement of molecules from high to low concentration; O2 moves into cells, CO2 out by simple diffusion through the lipid membrane.
    • Facilitated diffusion: diffusion with carrier proteins (e.g., glucose entry).
    • Osmosis: movement of water through a semipermeable membrane from region of low solute concentration (high solvent) to high solute concentration (low solvent); water moves continuously; osmotic pressure is the pressure needed to stop water flow.
    • Filtration: substances forced through a membrane by hydrostatic pressure; small solutes pass, larger molecules do not; important in kidney function.

  • Active processes (require energy)

    • Endocytosis: materials enter the cell.
    • Phagocytosis (cell eating): membrane extends around solid particles; some WBCs and macrophages are phagocytic.
    • Pinocytosis (bulk-phase): membrane extends around fluid droplets; important in intestinal absorptive cells.
    • Receptor-mediated endocytosis: receptors bind specific substances (enzymes, insulin, hormones, iron, cholesterol).
    • Exocytosis: materials expelled; waste excreted; useful products secreted.
    • Active transport: moves molecules from low to high concentration with carrier proteins; Na+/K+ pump is a key example.
    • Hypotonic, hypertonic, isotonic solutions describe extracellular vs intracellular solute concentrations:
    • Hypotonic: extracellular fluid less concentrated than intracellular; RBCs may lyse (hemolysis).
    • Hypertonic: extracellular fluid more concentrated; RBCs crenate.
    • Isotonic: equal concentrations; cells remain unchanged.

Tissues

  • Tissue: groups of similar cells with related functions.

  • Histology: microanatomy; study of tissues.

  • Four primary tissue types:

    • Epithelial
    • Connective
    • Muscle
    • Nervous

  • Epithelial tissue

    • Covers body surfaces, lines cavities, forms active parts of glands.
    • Functions: protection, secretion, excretion, filtration, absorption, sensory reception.
    • Can be simple (one cell layer) or stratified (multiple layers).
    • Subtypes:
    • Squamous epithelium: flat cells; simple squamous lines vessels and alveoli; stratified squamous lines mouth, esophagus, vagina, rectum; keratinized epidermis and nonkeratinized mucosa.
    • Cuboidal epithelium: cube-shaped; simple cuboidal for absorption/secretion (kidney tubules, glands); stratified cuboidal lines some ducts.
    • Columnar epithelium: tall cells; simple columnar for absorption/secretion with microvilli and goblet cells; ciliated columnar lines bronchi, uterine tubes, uterus; stratified columnar in some ducts.
    • Pseudostratified columnar epithelium: appears multi-layered but all cells touch basement membrane; usually ciliated with goblet cells; respiratory tract.
    • Transitional (uroepithelium): varies with organ distention; cuboidal when bladder empty, squamous when full; urinary tract.
    • Glandular epithelia: endocrine (ductless; secrete into bloodstream) vs exocrine (ducts; secrete onto surfaces).

  • Connective tissue

    • Elements: cells, fibers, and matrix (ground substance).
    • Functions: connects, supports, protects, insulates, transports fluids, stores energy.
    • Fiber types: collagen (white; strong), elastic (yellow; elastin), reticular (fine network).
    • Cell types: immature (-blast), mature (-cyte), and those that break substances down (-clast).
    • Connective tissue types are divided into connective tissue proper and specialized connective tissue.

  • Muscle and Nervous Tissues

    • Muscle tissue: skeletal (striated, voluntary), smooth (visceral, involuntary), cardiac (involuntary, in heart).
    • Nervous tissue: neurons (conduct impulses) and neuroglial (glial) cells (supporting, do not conduct impulses).

  • Membranes

    • Membranes combine epithelium with connective tissue.
    • Types:
    • Mucous membranes (mucosae): line hollow organs; absorb, secrete mucus; often stratified squamous or simple columnar; color can indicate health (e.g., blue = hypoxia).
    • Serous membranes (serosa): line body cavities, not exterior; simple squamous over loose connective tissue; secrete serous fluid to reduce friction (locations named as parietal vs visceral, e.g., pericardium, pleura, peritoneum).
    • Cutaneous membranes (integument/skin): keratinized stratified squamous epithelium (epidermis) over dense irregular connective tissue (dermis).

  • Body Orientation Terms (brief references)

    • Proximal/distal, Anterior/Posterior, Palmar/Plantar, Superficial/Deep.

Skeletal System

  • Osteology: study of bones.

  • Skeletal divisions:

    • Axial skeleton: bones along the midline (ribs, skull, vertebral column, sternum).
    • Appendicular skeleton: bones of the limbs (e.g., femur, humerus).

  • Bone functions: support soft tissues, protect organs, act as levers for muscles, store minerals, produce blood cells.

  • Bone types:

    • Compact (dense) bone: few spaces; strong; haversian systems (osteons) with central canal, canaliculi, lamellae, lacunae.
    • Spongy (cancellous) bone: no haversian systems; trabeculae with marrow in spaces; skull bone contains diploë.

  • Bone cells:

    • Osteoblasts: immature; produce bone matrix (osteoid).
    • Osteocytes: mature bone cells occupying lacunae.
    • Osteoclasts: large, multinucleated cells that resorb bone; essential for remodeling; balance osteoblast/osteoclast activity.

  • Classification of bones:

    • Long bones: shaft (diaphysis), ends (epiphyses), marrow cavity; examples: radius, femur; parts include periosteum, endosteum, articular cartilage, and epiphyseal cartilage (growth plate).
    • Short bones: cube-shaped; compact bone with spongy center; function as shock absorbers (e.g., carpus, tarsus).
    • Flat bones: two layers of compact bone with spongy bone in between; protect; examples: pelvis, scapula, ribs, skull bones.
    • Pneumatic bones: contain sinuses (e.g., frontal).
    • Irregular bones: complex shapes (vertebrae, some skull bones).
    • Sesamoid bones: small bones within tendons near joints; reduce friction (e.g., patella).

  • Ossification (osteogenesis)

    • Endochondral ossification: bones formed from cartilage models; majority of bones.
    • Intramembranous ossification: bones formed from fibrous membranes; most flat bones.

  • Species differences (vertebral formulas) and others:

    • Cat has clavicle; dog typically does not.
    • Male dogs and cats have a baculum/os penis; cattle have os cordis in the heart.

  • Joints (Articulations)

    • Formed when two or more bones are connected by fibrous, elastic, or cartilaginous tissue.
    • Function-based classification:
    • Synarthrosis: immovable (e.g., skull sutures).
    • Amphiarthrosis: slightly movable (e.g., pubic symphysis).
    • Diarthrosis: freely movable (e.g., stifle); most joints are synovial with joint cavity, synovial membrane, and joint capsule.
    • Structure-based classification:
    • Fibrous: no joint cavity; sutures; immovable.
    • Cartilaginous: no joint cavity; intervertebral discs, pubic symphysis; slightly movable.
    • Synovial: joint cavity with synovial fluid; movable; includes various subtypes by structure.

  • Muscular System

    • Function: produces movement, maintains posture, generates heat.
    • Types:
    • Skeletal (striated, voluntary): long, parallel fibers; multinucleated; peripheral nuclei; sarcomeres; actin and myosin; Z line, M line, A band, I band, H zone.
    • Smooth (visceral, involuntary): spindle-shaped; single nucleus; found in walls of hollow organs; two types: single unit and multiunit.
    • Cardiac (myocardium): involuntary; branched; intercalated discs; coordinate contraction.
    • Sliding-filament mechanism (skeletal muscle):
    • Nerve impulse → acetylcholine release → sarcolemma → T-tubules → sarcoplasmic reticulum → Ca2+ release → troponin-tropomyosin shift → exposure of myosin-binding sites on actin → ATP provides energy for cross-bridge cycling → sarcomere shortening; relaxation requires Ca2+ re-sequestration; all-or-none rule for muscle fiber contraction.
    • Skeletal muscle actions:
    • Flexor (decreases joint angle)
    • Extensor (increases joint angle)
    • Abductor (away from midline)
    • Adductor (toward midline)
    • Levator (dorsal movement)
    • Depressor (ventral movement)
    • Sphincter (reduces opening size)

Nervous System

  • Central Nervous System (CNS): brain and spinal cord.

  • Brain anatomy:

    • Cerebrum: motor control, sensory interpretation, association areas; gray matter on outside, white matter inside; gyri/sulci increase surface area; longitudinal fissure separates hemispheres; four lobes (frontal, parietal, occipital, temporal).
    • Diencephalon: thalamus (sensory relay; temperature and pain), hypothalamus (homeostasis; temperature, fluids, thirst, urination, hunger, emotion; links to endocrine system).
    • Brainstem: midbrain, pons, medulla oblongata; respiration centers in pons; medulla controls respiration, heart rate, vomiting, coughing, sneezing; reticular activating system (RAS) in brainstem governs sleep/wake cycles.
    • Cerebellum: coordination and balance.

  • spinal cord: outer white matter (nerve fibers), inner gray matter (neuron cell bodies with butterfly shape); ascending (sensory) and descending (motor) tracts; conveys sensory input to brain and motor output from brain; protected by bone and meninges.

  • Meninges: protective coverings of CNS

    • Dura mater: outer tough fibrous layer
    • Arachnoid mater: delicate connective tissue layer
    • Pia mater: thin layer with blood vessels; adheres to brain/spinal cord
    • Epidural space: between bone and dura; contains fat, blood vessels, and connective tissue; site for anesthetic injection
    • Subarachnoid space: contains CSF and large vessels

  • CSF and blood-brain barrier

    • CSF: colorless fluid; cushions brain; provides nutrients; lumbar puncture used for sampling.
    • Blood-brain barrier: endothelial tight junctions prohibit most substances; lipid-soluble substances diffuse; glucose and amino acids require facilitated diffusion; protects brain from fluctuations.

  • Peripheral Nervous System (PNS)

    • Nerves connect CNS to body; divisions: afferent (sensory) and efferent (motor);
    • Somatic (voluntary) vs Autonomic (involuntary) nervous system; Autonomic splits into sympathetic (fight-or-flight) and parasympathetic (rest-and-digest).

  • Neurons and Neuroglia

    • Neuron: dendrites, cell body, axon; action potentials; all-or-none principle; one-way impulse transmission; limited regeneration.
    • Myelin and nodes of Ranvier give saltatory conduction (faster transmission).
    • Glial cells: CNS — astrocytes, oligodendrocytes, microglia, ependymal; PNS — Schwann cells, satellite cells; support and protection; not transmit impulses.

  • Reflexes

    • Reflex arc: stimulus → sensory neuron → interneuron or direct motor neuron → effector → response.
    • Examples: stretch reflex (knee-jerk), withdrawal reflex, corneal reflex, papillary light reflex.

  • Cardiovascular System (heart and vessels)

  • Heart structure and protective layers

    • Myocardium: cardiac muscle; intercalated discs permit synchronized contraction due to low electrical resistance.
    • Pericardium: double-walled sac; fibrous outer layer; serous inner layer with parietal and visceral layers; pericardial cavity contains pericardial fluid to reduce friction.
    • Endocardium: serous membrane lining inner chambers.

  • Circulation

    • Pulmonary circulation: precava (cranial) and postcava (caudal) return to right atrium; through tricuspid valve to right ventricle; through pulmonary semilunar valve to lungs; oxygenated blood returns via pulmonary veins.
    • Systemic (somatic) circulation: oxygenated blood to left atrium via pulmonary veins; through bicuspid (mitral) valve to left ventricle; out through aorta via aortic semilunar valve to body.
    • Major arteries branching from aortic arch in dogs/cats: innominate (brachiocephalic) to right subclavian and carotids; left subclavian arises separately.
    • Coronary circulation supplies myocardium; coronary veins remove waste.

  • Cardiac Cycle and Heart Sounds

    • Cardiac cycle: atrial systole with ventricular diastole; then ventricular systole with atrial diastole.
    • SA node initiates atrial contraction; impulse travels to AV node, bundle of His, Purkinje fibers; ventricles contract to push blood through semilunar valves.
    • Heart sounds: lub (AV valves close) and dupp (semilunar valves close); a brief pause between.

  • Heart Rate

    • Rates vary by age, size, breed, health, and hormones; typical ranges:
    • Dog: 70-160\,beats/min
    • Cat: 150-210\,beats/min
    • Horse: 28-50\,beats/min
    • Cattle: 40-80\,beats/min

  • ECG (electrocardiography)

    • P wave: atrial depolarization (atrial systole)
    • QRS complex: ventricular depolarization (ventricular systole)
    • T wave: ventricular repolarization (ventricular diastole)
    • Atrial diastole is masked by the QRS complex

  • Blood vessels and Blood Pressure

    • Arteries carry blood away from the heart; usually oxygenated (except pulmonary artery);
    • Arterioles regulate flow into capillaries; Capillaries: single endothelial layer; exchange of O2/CO2; Venules and veins return blood to the heart; veins have valves due to low pressure; blood pressure components: systolic (ventricular contraction) and diastolic (ventricular relaxation).

  • Fetal Circulation

    • In the fetus, lungs/kidneys/digestive tract nonfunctional; placenta provides nutrients/waste exchange; special shunts (foramen ovale, ductus arteriosus) direct blood flow; most blood bypasses lungs; after birth, shunts close.

Digestive System

  • General purpose: break down food into absorbable nutrients; species variations reflect diets.
  • Digestive processes: ingestion, mechanical/chemical digestion, peristalsis, absorption, defecation.
  • Diet types:
    • Herbivore: plants (e.g., rabbit, cattle, horse, sheep)
    • Carnivore: meat (e.g., cat, dog, tiger)
    • Omnivore: plants and meat (e.g., rats, pigs, humans)
  • Histological layers of GI tract: mucosa (epithelium, lamina propria, muscularis mucosae), submucosa, muscularis externa (oblique, circular, longitudinal layers where applicable), serosa.
  • Structures:
    • Mouth: mastication; bolus formation.
    • Pharynx: shared passage for digestive and respiratory systems.
    • Esophagus: muscular tube; peristalsis moves food to stomach.
    • Stomach (simple monogastric): regions include esophageal, cardiac, fundic, pyloric; fundic region contains glands with mucous neck cells, chief cells (pepsinogen), parietal cells (HCl), endocrine cells (gastrin); inner rugae; gastric juice makes chyme; pH acidic.
  • Stomach types
    • Monogastric stomachs (non-ruminant): four regions; rugae; acid pH; gastric glands.
    • Ruminant stomachs: four compartments — rumen, reticulum, omasum, abomasum; function in fermentation and digestion of plant material; regurgitation and rechewing (eructation), digestion with microbial fermentation.
  • Small intestine
    • Regions: duodenum, jejunum, ileum; major site of digestion and absorption.
    • Structures increasing surface area: circular folds, villi, microvilli.
    • Enzymes: digestive enzymes secreted by pancreas (proteases, amylases, lipase) and intestinal enzymes (peptidases, maltase, sucrase, lactase, nucleases).
    • Pancreatic enzymes delivered in an alkaline fluid to neutralize chyme.
    • Nutrient absorption: monosaccharides and amino acids absorbed into capillaries; fats absorbed into lacteals of villi.
  • Large intestine
    • Cecum at ileocecocolic junction; colon (ascending, transverse, descending);
    • No villi; goblet cells produce mucus; absorbs water; synthesizes vitamins B and K; moves waste toward rectum.
  • Rectum and anus
    • Rectum ends large intestine; secretes mucus; anus with internal (involuntary) and external (voluntary) sphincters.
  • Accessory organs
    • Pancreas: neutralizes chyme with sodium bicarbonate; produces digestive enzymes (trypsin for proteins, lipase for fats, amylase for starch).
    • Liver: bile production for fat emulsification.
    • Gallbladder: stores bile; releases into duodenum in response to cholecystokinin (CCK); note: rats and horses lack a gallbladder.
  • Digestive process (simple stomach)
    • Mouth: salivary amylase begins starch digestion.
    • Stomach: gastric juice contains protein-digesting enzymes, HCl, mucus; rennin (chymosin) in young animals coagulates milk.
    • Small intestine: pancreatic enzymes (amylase, trypsin, chymotrypsin, elastase, peptidases, lipase, nucleases); pancreatic secretions are alkaline to neutralize chyme; intestinal enzymes (trypsin, maltase, sucrase, lactase, nucleases).
    • Segmentation and peristalsis mix chyme and move it along; absorption of monosaccharides and amino acids into capillaries; fats into lacteals.
    • Large intestine absorbs water, synthesizes vitamins, and forms/expels feces via defecation.

Lymphatic System

  • Function: absorbs protein-containing fluid from capillaries, returns it to venous system; transports dietary fats from digestive tract to blood; produces lymphocytes and develops immunity.
  • Structure:
    • Lymph vessels: blind-ended tubes; parallel to venous system; valves; lymph is filtered through lymph nodes.
    • Lymph nodes: filter lymph; produce lymphocytes.
    • Lymph organs: spleen (phagocytic, stores blood, produces lymphocytes), tonsils (lymphoid tissue in mucous membranes), thymus (develops immune response in young; may be replaced by fat in adults).

Respiratory System

  • Structures:
    • Nostrils (nares); nasal cavity with turbinate bones; air warmed, moistened, filtered.
    • Pharynx: nasopharynx, oropharynx, laryngopharynx; Eustachian tube.
    • Larynx: cartilage (thyroid, cricoid, arytenoid, epiglottis); epiglottis covers glottis during swallowing; vocal folds attach to arytenoid cartilage.
    • Trachea: C-shaped cartilaginous rings; lined with ciliated columnar epithelium; bifurcates into bronchi.
    • Bronchi: right and left; cartilaginous; branches become bronchioles (less cartilage).
    • Lungs: lobes vary by species; covered by visceral pleura; contain alveoli where gas exchange occurs.
  • Physiology: respiration comprises ventilation (air movement), external respiration (gas exchange at alveoli), and internal respiration (gas exchange at tissues).
  • Ventilation mechanics:
    • Inspiration: diaphragm and external intercostals contract; thoracic cavity enlarges; intrathoracic and intra-alveolar pressures fall; air enters.
    • Expiration: muscles relax; thoracic cavity decreases; air exits; expiration is passive.
  • Lung volumes (typical references): tidal volume, inspiratory/expiratory reserve volumes, residual volume, dead space.
  • Respiratory rates (example species):
    • Dog: 10-30\text{ breaths/min}
    • Cat: 24-42\text{ breaths/min}
    • Horse: 8-16\text{ breaths/min}
    • Cattle: 12-36\text{ breaths/min}
  • Control of respiration and terminology:
    • Medullary rhythmicity center (in medulla) with inspiratory/expiratory neurons.
    • Apneustic area (pons) prolongs inspiration; pneumotaxic area (pons) inhibits apneustic area to promote expiration.
    • Hering-Breuer reflex prevents overinflation.
    • CO₂ levels influence respiratory rate; other factors include pain, temperature, pH, oxygen, and stress.
    • Terminology: pneumothorax, atelectasis, pleuritis, pneumonia, eupnea, dyspnea, apnea.

Excretory System

  • Kidneys: remove metabolic waste from blood; essential for blood pressure regulation; bean-shaped in many species; renal corpuscle (nephron) is the functional unit.
  • Internal anatomy:
    • Cortex contains glomerulus, Bowman's capsule, proximal and distal tubules.
    • Medulla contains Loop of Henle and collecting tubules; medulla organized into pyramids; papilla opens to minor calyx, then major calyx, renal pelvis.
  • Ureters: smooth muscle; peristalsis moves urine to bladder.
  • Urinary bladder: smooth muscle; lined with transitional epithelium.
  • Urethra: smooth muscle tube to exterior.
  • Physiology of urine formation:
    • Filtration: blood enters glomerulus via afferent arteriole; water, salts, and small molecules pass into Bowman's capsule to form filtrate; glomerular filtration rate (GFR).
    • Reabsorption: substances needed by the body are reabsorbed from filtrate in PCT and loop of Henle into peritubular capillaries.
    • Secretion: substances are secreted from peritubular capillaries into the distal tubule.
    • Micturition: urine flow from collecting ducts to renal pelvis, ureter, bladder, and urethra; urination.
  • Hormonal regulation of water/salt balance:
    • Antidiuretic hormone (ADH/vasopressin): increases water reabsorption in kidneys.
    • Aldosterone: promotes sodium reabsorption in kidneys.

Reproductive System

  • Male anatomy

    • Testicles: paired oval glands in a scrotum; seminiferous tubules produce sperm; interstitial cells of Leydig produce testosterone.
    • Epididymis: maturation and storage of sperm; connects seminiferous tubules to vas deferens.
    • Vas deferens (ductus deferens): carries sperm; part of the spermatic cord with vessels and nerves; passes through inguinal ring; joins the urethra.
    • Accessory sex glands: glands produce semen; roles include transporting sperm, protecting sperm in female acidic environment, and providing nutrition.
    • Species variation: dogs have prostate only in accessory glands; cats have prostate and bulbourethral glands; stallions have vesicular glands, prostate, bulbourethral glands, and ampulla; some species have baculum (os penis) in the penis; dog penis has a long glans; cat penis is retracted and has spines.
    • Hormonal control during male reproduction: FSH stimulates spermatogenesis; ICSH (LH) stimulates testosterone production by Leydig cells.

  • Female anatomy

    • Ovaries: paired oval organs producing ova and hormones.
    • Oviducts: conduct ova from ovaries to uterine horns/uterus; infundibulum guides ovum into oviduct.
    • Uterine horns/uterus: species variation in horn presence; in mono-/uni-parous animals, embryos develop in body of uterus; in poly-/multiparous animals, embryos develop in uterine horns.
    • Cervix: opening to uterus; some species have double cervix.
    • Vagina, vestibule, and vulva: reproductive tract structures; vestibule is common duct for urine and birth.
    • Histology: endometrium (epithelium, mucous membrane, glands; cycle-dependent thickness; reabsorbed in estrous species; sloughed in menstrual species), myometrium (smooth muscle), perimetrium (serous covering).

  • Estrous cycle variations

    • Types: monoestrous, diestrous, polyestrous; seasonally polyestrous; induced ovulators (cat, rabbit, mink, ferret) vs spontaneous ovulators (dog, cattle, horse).
    • Phases:
    • Proestrus: follicle growth; estrogen rises; uterus prepares; not receptive; FSH influence; follicles mature.
    • Estrus (standing heat): female receptive; LH triggers ovulation in dogs; cats/rabbits are induced ovulators; behavior changes occur in dogs/cats.
    • Metestrus: post-ovulation; corpus luteum forms; progesterone rises; uterine maturation; inhibition of new follicle development.
    • Diestrus: CL secretes hormones; if not pregnant, CL degenerates; if pregnant, CL may be maintained depending on species; pseudopregnancy can occur.
    • Anestrus: prolonged inactivity in seasonally polyestrous animals.

  • Fertilization and pregnancy

    • Copulation introduces semen; fertilization occurs in oviduct.
    • Zygote undergoes mitotic divisions; implants in uterus/horns depending on species.
    • Fetal membranes protect embryo; placenta forms to enable nutrient/waste exchange without mixing maternal and fetal blood.
    • Between implantation and birth, developing organism is called a fetus.
    • Fetal membranes: amnion (amniotic fluid), allantois (fluid-filled; adsorbs waste; forms part of placenta), chorion (outermost; attaches to endometrium).

  • Parturition and lactation

    • Labor: oxytocin triggers uterine contractions; fetus delivered through cervix and vagina; placenta delivered after birth.
    • Gestation periods (approximate): cat/dog ~63 days; horse ~336 days; cow ~285 days.
    • Dystocia: difficult birth; potential maternal/fetal causes; cesarean may be needed.
    • Lactation: milk production begins with colostrum (antibodies, proteins, vitamins); regulated by prolactin.

Endocrine System

  • Endocrine glands are ductless and secrete hormones directly into the bloodstream.
  • Hormone actions: can alter membrane permeability, organelle permeability, enzyme activity, and rate of enzyme production.
  • Regulation: most hormonal secretion is governed by negative feedback; adrenal medulla is under neural control.

Integumentary System

  • Skin structure: two layers of skin and an underlying subcutaneous layer.

  • Epidermis: multiple strata; from outermost stratum corneum (keratinized, shed and replaced) to stratum basale (mitotically active with melanocytes).

  • Dermis (corium): thick layer containing vessels, nerves, and glands.

  • Hypodermis: subcutaneous tissue with connective and adipose tissue.

  • Hair anatomy: medulla, cortex, cuticle; hair growth from follicles; arrector pili muscles raise hairs; hair types include guard hair, wool hair, tactile (sinus) hairs; horn-like structures (horns, claws, hooves) arise from specialized dermis.

  • Sense organs in skin: Meissner’s corpuscles, Ruffini endings, Pacinian corpuscles, and various glands; melanocytes produce skin color.

  • Specialized integument: horns, claws, hooves.

  • Eye anatomy (sense organ):

    • Sclera: outer white layer.
    • Uvea: vascular layer including iris (color), ciliary body (aqueous humor production), choroid.
    • Retina: photoreceptors (rods and cones).
    • Lens and vitreous humor; pupil; cornea; conjunctiva; nictitating membrane (third eyelid).
    • Lacrimal apparatus: lacrimal gland secretes tears; tears drain via nasolacrimal duct.

  • Eye physiology: light passes through pupil, is focused by lens, and stimulates rods/cones; impulses travel via optic nerve to brain; rods function in dim light; cones function in bright light and color.

  • Ear (hearing) anatomy

    • Outer ear: pinna to tympanic membrane.
    • Middle ear: tympanic cavity with three auditory ossicles — malleus, incus, stapes; air-filled; communicates with nasopharynx via Eustachian tube.
    • Inner ear: cochlea (hearing) and semicircular canals (balance).

  • Hearing physiology: sound transmits through outer ear to tympanic membrane; ossicles amplify and convey to the oval window; cochlea organ of Corti transduces to nerve impulses; round window accommodates fluid movement.

  • Deafness types: nerve deafness (receptors or auditory nerve dysfunction) vs transmission deafness (sound transmission failure).

  • Senses: smell and taste

    • Smell: olfactory receptors in nasal cavity; olfactory bulb processes signals.
    • Taste: gustatory papillae on tongue; types include fungiform, foliate, vallate; contain taste buds; horse has mucous glands in tongue; filiform and conical papillae provide mechanical functions (directing food, grooming, lapping).

  • Overview of the Nervous and Sense Organs (connections to exam-style items)

    • Key structures and terms frequently tested include: neuron structure, glial cells, reflex arcs, brain anatomy (cerebrum, thalamus, hypothalamus, brainstem, cerebellum), CSF, blood-brain barrier, myelin, nodes of Ranvier, organ of Corti, retina layers, and auditory/visual pathways.

Review and Connections

  • Core themes across systems include: integration of structure and function; energy use (ATP production); cellular transport and membrane dynamics; multi-level organization from cells to organs to systems; homeostasis via feedback mechanisms; and species variations relevant to clinical practice.
  • Practical implications include understanding how anatomy informs radiographic positioning, surgical approaches, catheter placement, anesthesia considerations, and interpretation of clinical signs (e.g., mucous membrane color indicating hypoxia).
  • Ethical/philosophical/practical considerations: knowledge of anatomy and physiology underpins animal welfare decisions, accurate diagnosis, appropriate treatment planning, and humane handling during veterinary procedures.

Quick Reference Highlights (Pared-Down)

  • Nuclear and organelle basics: nucleus, mitochondria (ATP), ER (RER vs SER), Golgi, lysosomes, peroxisomes, cytoskeleton, centrioles.

  • Membrane transport: diffusion, osmosis, facilitated diffusion, filtration, endocytosis (phagocytosis, pinocytosis, receptor-mediated), exocytosis, active transport (Na+/K+ pump).

  • Four tissues and main subtypes: epithelial (squamous, cuboidal, columnar; mucous/serous membranes; glands), connective (fibers, ground substance; proper vs specialized), muscle (skeletal, smooth, cardiac; sliding filament theory), nervous (neurons, glia).

  • Skeletal system concepts: bone types (compact vs spongy), osteoblasts/cyte/clast, ossification (endochondral and intramembranous), bone classifications (long, short, flat, pneumatic, irregular, sesamoids), joints (fibrous, cartilaginous, synovial), and species differences (clavicle presence, baculum).

  • Cardiovascular basics: heart structure and sounds; cardiac cycle; ECG basics; vessel types (arteries, arterioles, capillaries, venules, veins); fetal circulation shunts.

  • Digestive overview: monogastric vs ruminant; GI tract layers; stages of digestion and enzyme sources; absorption sites; liver/gallbladder/pancreas roles.

  • Respiratory mechanics and physiology: ventilation, gas exchange, lung volumes, and control centers; common terms and disorders.

  • Excretory system essentials: nephron anatomy; filtration/reabsorption/secretions; urine flow; ADH and aldosterone roles.

  • Reproductive system layout: male and female anatomy and hormones; estrous vs menstrual cycles; fertilization, pregnancy, parturition, lactation.

  • Integumentary senses and anatomical features: skin layers, hair, glands, sense receptors, eye components, ear anatomy.

  • Symbols and terms you should be able to place in context (examples):

    • Z ext{ line}, M ext{ line}, A ext{ band}, I ext{ band}, H ext{ zone} in relation to the skeletal muscle sarcomere.
    • SA ext{ node}
      ightarrow AV ext{ node}
      ightarrow ext{bundle of His}
      ightarrow ext{Purkinje fibers}
      ightarrow ext{ventricular contraction} in the cardiac conduction pathway.
    • P ext{ wave}, QRS complex, T ext{ wave} for ECG interpretation.
    • Foramen ovale and ductus arteriosus in fetal circulation shunting and postnatal closure.

  • Notes on language and testing tips

    • Be comfortable with terminology for orientation (proximal/distal, anterior/posterior, dorsal/ventral) and with directional terms related to limbs.
    • Expect questions on functional relationships (e.g., how osmosis relates to red blood cell integrity under different tonicity, or how the CRISPR-like conceptual of organelle roles might be tested via clinical scenarios).