Vertebrate Anatomy Study Notes

Vertebrate Anatomy Study Notes

Instructor Information

  • Course: Vertebrate Anatomy (ABCS 205)
  • Instructor: Prof. F. Gbogbo
  • Office: No. 44 DABCS
  • Email: fgbogbo@ug.edu.gh

Introduction to Anatomy

  • Definition: The study of external and internal structure of an organism to gain insight on how an organism is built.
    • Purpose of Anatomy:
    • Helps in understanding phylogeny and evolution.
    • Resolves taxonomic problems.

Course Content Overview

  • Introduction to Vertebrate Anatomy.
  • Functional Anatomy of:
    • Bony Fish
    • Amphibians
    • Reptiles
    • Birds
    • Mammals.

Course Objectives

  • Students will be able to:
    • Utilize common anatomical terms to describe positions in anatomy.
    • Differentiate between characteristics of major classes of vertebrates.
    • Discuss anatomical differences among major classes of vertebrates.
    • Explain relationships between the structure and function of major organs and systems in vertebrate classes.

Assessment & Components

  • Continuous Assessment (C.A.): 30%
  • Final Exam: 70%

Recommended Textbooks

  • The Diversity of Fishes (2nd Edition) by Gene S. Helfman, Bruce B. Collette, Douglas E. Facey, Brian W. Bowen.
    • Publisher: WILEY-BLACKWELL.
  • Herpetology (3rd Edition) by Laurie J. Vitt, Janalee P. Caldwell.
    • Manual of Ornithology by Noble S. Proctor & Patrick J. Lynch.
  • Mammalogy by George A. Feldhamer, Lee C. Drickamer, Stephen H. Vessey, Joseph F. Merritt, Carey Krajewski.

Chordates Overview

  • Characteristics of Chordates:
    1. Notochord.
    2. Dorsal hollow nerve cord.
    3. Pharyngeal gill slits.
    4. Post-anal tail.
Notochord
  • Description:
    • A flexible rod-like structure made of vacuolated cells encased by a fibrous sheath.
    • Located between the digestive tract and the central nervous system.
    • Function:
    • Permits undulatory movements.
    • Resists shortening during movement.
    • Serves as an axis for muscle attachment.
Dorsal Hollow Nerve Cord
  • Differences between chordates and non-chordates:
    • Position: Non-chordates have a ventral nerve cord, whereas chordates have a dorsal one.
    • Form: Non-chordates possess a solid nerve cord, while chordates have a tubular, hollow one.
Pharyngeal Gill Slits
  • Description:
    • Slit-like openings leading from the pharyngeal cavity to the outside.
    • Present during the embryonic stage in all chordates and may persist or disappear in adulthood.
    • Importance:
    • Allow water intake via the mouth to exit without traversing the entire digestive tract.
Post-Anal Tail
  • Description:
    • Muscular extension beyond the anus.
    • Importance:
    • Primarily for propulsion in water.

Types of Chordates

  1. Protochordates
    • Notochord either persists or degenerates over time.
  2. Vertebrates
    • Notochord replaced by a spinal column (cartilage or bone).
    • Brain protected by a cranium.
    • Approximately 43,700 living species.

Classification of Vertebrates

  • Phylum: Chordata
  • Sub-Phylum: Vertebrata
  • Classes:
    1. Agnatha
    2. Chondrichthyes (Fishes)
    3. Osteichthyes
    4. Amphibia
    5. Reptilia
    6. Aves
    7. Mammalia

Fish Definition

  • Aquatic vertebrates with gills and limbs in the form of fins.
    • Characteristics:
    • Poikilothermic aquatic chordates.
    • Appendages, when present, developed as fins.
    • Major respiratory organs are gills.
    • Body covered with scales.
    • Complications in Definitions:
    • Eel-shaped fishes may lack fins/scales.
    • Tunas and lamnid sharks are homeothermic.
    • Lungfish and others possess lungs.
Diversity of Fishes
  • Statistics:
    • 62 orders.
    • 515 families.
    • 27,977 living species of fish.
    • 108 species are jawless (70 hagfishes & 38 lampreys).
    • 970 species of sharks.
    • 403 species of skates.
    • 534 species of rays.
    • 33 species of chimaeras.
    • Over 26,000 bony fishes.
Agnatha (Jawless Fish)
  • Characteristics:
    • No true jaws, internal ossifications, or scales.
    • Pairless fins; eel-like body forms; single medial nostril; pore-like gill openings.
    • Adults possess a hood-shaped buccal funnel fringed with sensory papillae.
    • Examples:
    • Two types: Lamprey and Hagfish.
      • Lamprey: Two dorsal fins, caudal fin, single nostril between the eyes.
      • Hagfish: Lacks dorsal fins, single nostril on the snout.
Cardiovascular System of Fishes
  • Description:
    • A system of arteries, veins, and capillaries transporting respiratory gases, nutrients, and waste.
  • Types:
    • Basic Pattern:
    • Single circuit system; heart pumps once per cycle with a two-chamber heart.
    • Tetrapod Heart:
    • Dual pump with a double circuit system; blood passes through the heart twice.
  • Structure:
    • Heart located posterior and ventral to gills; comprised of two chambers (one atrium, one ventricle).
  • Flow Pattern:
    • Blood from cardinal vein enters the sinus venosus, flows into atrium, then into the ventricle, exiting through the conus or bulbus arteriosus.
Agnatha Circulatory Specializations
  • Hagfish with Accessory Hearts:
    • Portal heart: blood from intestine to liver.
    • Cardinal heart: helps propel blood to sinus venosus.
    • Caudal heart: paired expansions in the caudal vein.
Digestive System of Agnatha
  • Key Features:
    • Lacks stomach, with a straight intestine containing folds (typhlosole).
    • Anticoagulants secreted into wounds for blood flow maintenance.

Chondrichthyes (Cartilaginous Fishes)

  • Characteristics:
    • Endoskeleton made of cartilage; have paired and unpaired fins.
  • Paired Fins:
    • Pectoral fins for direction control & pelvic fins for stability (males have claspers).
  • Unpaired Fins:
    • Dorsal fins for stability, anal fin for stabilization, and a caudal fin.
    • Mouth is ventral with teeth embedded in gums.
    • External Features:
    • Teeth are not fused with the skull; placoid scales present.
    • Cade of external gill slits (5-7 openings on each side).
  • Subclasses:
    1. Elasmobranchii (sharks, rays).
    2. Holocephali (chimeras).
  • Reproductive Features:
    • Internal fertilization with unique mating behaviors and organs.

Digestive System of Chondrichthyes

  • Structure:
    • Consists of mouth, buccal cavity, foregut (esophagus, stomach), midgut (intestine), and hindgut (rectum).
  • Components:
    • No true stomach in chimeras; gizzard structure for crocodiles.
    • Pancreatic duct and bile ducts connected to the duodenum.

Osteichthyes (Bony Fishes)

  • External Features:
    • Laterally flattened body with median and paired fins.
    • Caudal fin is typically homocercal, and gills covered with an operculum.
    • Skin covered with dermal scales; possess swim bladders for buoyancy.
  • Blood Flow Through Gills:
    • Highly efficient; consists of gill arches, rakers, and filaments for oxygen exchange via countercurrent exchange.
Buoyancy Regulation in Fishes
  • Definition: The ability to float is influenced by the action of gravity and buoyancy forces.
  • Swim Bladder: Gas-filled sac that regulates buoyancy by altering gas volume inside.
    • Physostomous: Connection between swim bladder and digestive tract.
    • Physoclisti: No connection; gas introduced through the gas gland.

Nervous System of Vertebrates

  • Structure:
    1. Central Nervous System (CNS): Brain and spinal cord.
    2. Peripheral Nervous System (PNS): Cranial nerves and spinal nerves.
    3. Autonomic Nervous System: Sympathetic and parasympathetic divisions.

Circulation & Respiration in Fishes

  • Cardiac Structure:
    • Two chambers (atrium & ventricle).
    • Systolic function in a single circuit system.
  • Oxygen Extraction in Gills: Featured by numerous oral and gill structures allowing effective gas diffusion.

Amphibians Overview

  • Description: Amphibians have soft, moist skin and undergo indirect development with aquatic larval stages.
  • Life Cycle Characteristics: Laying gelatinous eggs in water; metamorphosis into a terrestrial adult.
  • Respiration: Gas exchange occurs through the skin and lungs during adult stages.
Types of Amphibians
  1. Anura (Salientia): Frogs and toads.
    • Tailless adults, includes unique skeletal adaptations such as fused radius and ulna (radioulna).
  2. Urodela (Caudata): Salamanders and newts with well-developed tails.
  3. Apoda (Gymnophiona): Caecilians are limbless and have elongated bodies with annuli.

Reptiles

  • Classification Overview:
    • Four extant orders: Chelonia, Squamata, Crocodilia, Sphenodonta.
  • Evolution: Arisen from amphibians; successful land vertebrates through adaptations including amniotic eggs.
  • Adaptations for Terrestrial Life: Include tough skin, efficient lungs, and excretion of uric acid.
Reptile Anatomy Characteristics
  • Skin: Tough, dry, scaly with periodic shedding; differentiated into pairs of limbs, efficient designed jaws, and varying respiratory systems.
  • Circulatory and Nervous Systems: Functionally adapted to protect against dehydration, with some species exhibiting complete circulatory separation and adaptations for environmental conditions.