Animal Physiology and Comparative Anatomy Systems

Comparative Animal Physiology and Anatomy Systems

Circulatory and Vascular Systems

Diffusion in unicellular and multicellular organisms occurs across vascular diffusion channels (1 mm). Sponges utilize cavities and choanocytes, while cnidarians possess a digestive respiratory cavity known as the gastrovascular cavity, featuring one pore and ciliary cells. Flatworms utilize a similar cavity with two pores acting as a gastrovascular unit of fluid flux.

Circulatory System Types

• Open System: Found in arthropods and mollusks (hemolymph), featuring arteries and veins.
• Closed System: Specialized vascular systems containing blood and lymph, operating with afferent and efferent vessels.

Respiratory Pigments and Fluids

• Hemocyanin: Found in mollusks and arthropods.
• Chlorocruorin: Found in polychaete annelids.
• Hemoerythrin: Found in annelids and mollusks.
• Hemoglobin: Found in various taxa.

Heart Types by Contraction Mechanism

• Neurogenic: Smooth muscle nodal contraction driven by nerve tissue (annelids and arthropods).
• Myogenic: Cardiac muscle responding to muscle stimuli and cell morphology:
  • Tubular contractile hearts with valves ensuring unidirectional pumping (arthropods).
  • Tunics with bidirectional non-pumping valves.
  • Accessory hearts featuring ampoule forms, valves, and branchial structures.
  • Compartmentalized hearts with atria (receiving hemolymph) and ventricles (expelling hemolymph) equipped with valves.

Vertebrate Heart Configurations

• Fish: 1 atrium and 1 ventricle.
• Amphibians: 2 atria and 1 ventricle.
• Reptiles: 2 atria and 1 ventricle (except Crocodilia, which possess complete septa and 2 atria and 2 ventricles).
• Birds and Mammals: 2 atria and 2 ventricles.

Immune and Defense Mechanisms

Pathogens face multiple biological barriers:

• First Barrier: Skin, mucous membranes, and bacterial flora (nonspecific).
• Second Barrier: Humoral factors, phagocytic cells, and NK cells (nonspecific).
• Third Barrier: B and T lymphocytes (specific/adaptive immunity).

Respiratory System

Nasal Cavity

• Vestibule: Non-keratinized stratified squamous epithelium with hairs and mucus.
• Respiratory Segment: Ciliated pseudostratified epithelium with seromucous secretion and goblet cells, filtering, warming, and humidifying air.
• Olfactory Segment: Olfactory epithelium containing olfactory, supporting, and basal cells.

Pharynx and Trachea

• Pharynx: Cartilage, flat pseudociliated epithelial plates.
• Trachea: Ciliated lamina propria, loose connective tissue with capillaries, lymphatics, and glands, horseshoe-shaped tracheal cartilage, and adventitia.

Excretory and Osmoregulatory Systems

Aquatic animals manage osmoregulation differently: osmoregulators maintain an internal osmotic pressure distinct from the environment, whereas osmoconformers match the environmental osmolarity.

Excretory Structures

• Protonephridia: Small acoelomates, blind external system of tubules with flame bulbs.
• Metanephridia: Long twisted tubules connecting internal and external environments, associated with capillary beds for reabsorption.
• Malpighian Tubules: Thin blind filtering tubules in insects processing wastes from hemolymph lacunae.
• Green/Antennal Glands: Blind saccules with a single tube and bladder, filtering hemolymph.
• Pronephros: Primitive kidney with a single glomerulus allowing plasma to pass near nephrostomes and reabsorbable tubules.
• Mesonephros: Associated glomerular epithelium passing products to renal corpuscles and tubules.
• Nephron: Glomerulus surrounded by an epithelial capsule, composed of mesangial cells.

Juxtaglomerular Apparatus

Extraglomerular cells and a portion of the distal convoluted tubule detect sodium levels and blood pressure, releasing renin to influence angiotensinogen pathways.

Renal and Urinary Anatomy

Kidneys feature nephrons and can be monolobed or polylobulated. The ureters and bladder feature urothelium. The urinary bladder lacks a submucosa or muscularis mucosae, possessing two muscular layers (inner longitudinal, outer circular). Glands include eccrine and apocrine sweat glands, alongside the liver excreting bilirubin and biliverdin.

Digestive System

The digestive tract comprises the mucosa (epithelium, lamina propria, muscularis mucosae), submucosa, muscular layer (circular and longitudinal), and a double adventitia (parietal and visceral).

Teeth Anatomy

• Hard Tissues: Dentin (produced by odontoblasts), enamel (covering the crown, produced by ameloblasts), and cementum (covering the root, produced by cementoblasts).
• Soft Tissues: Dental pulp (nourishing the dental cavity) and the periodontal membrane (anchoring roots to bone via collagen fibers).

Gums and Papillae

Gums contain three cell types:

• Neuroepithelial cells (sensory, non-synaptic axons).
• Supporting cells with microvilli.
• Basal cells (undifferentiated with a high renewal rate).

Digestive Organs

• Esophagus: Straight muscular tube with non-keratinized stratified epithelium, mucous glands, and two muscle layers.
• Stomach: Cardia (simple columnar epithelium with mucous glands), central zone (specialized mucosa with crypts), and pylorus (transitional epithelium).
• Pancreas: Exocrine acinar structure with protein secretion, and endocrine islets producing insulin and glucagon.

Nervous System and Nerve Fibers

The nervous system consists of sensory receptors (capturing information), an integrator (processing information), and motor components (transmitting responses to muscles). It is divided into the Central Nervous System (brain, brainstem, spinal cord) and the Peripheral Nervous System (nerves, ganglia, nerve plexuses).

Nerve Fiber Types

• Type A: Heavily myelinated, thick axon, rapid transmission.
• Type B: Heavily myelinated, fine axon.
• Type C: Unmyelinated, fine axon, slow transmission.