Tissue Histology and Comparative Vertebrate Anatomy: Study Guide

Laboratory 8: Tissue Histology

Introduction to Tissues

Tissues are groups of cells with a specific function in the body. In animals, there are four basic types of tissues: epithelial, connective, muscular, and nervous. Each tissue type is specialized for particular roles and forms the foundation for organ structure and function. Organs are composed of multiple tissue types working together to perform complex biological functions.

Organ System	Main Function	Principal Organs
Integumentary	Protection, temperature regulation	Skin, hair, nails
Muscular	Movement, heat production	Skeletal muscles
Skeletal	Support, protection, blood formation	Bones, cartilage
Nervous	Coordination, control	Brain, spinal cord, nerves
Cardiovascular	Transport of substances	Heart, blood vessels
Respiratory	Gas exchange	Lungs, trachea
Digestive	Breakdown and absorption of food	Stomach, intestines
Urinary	Excretion of wastes	Kidneys, bladder
Reproductive	Production of offspring	Ovaries, testes

Objectives

• Examine the structure and function of the four tissue types in animals.

• Identify tissues under the microscope and relate structure to function.

• Describe the relationship between tissues, organs, and organ systems.

A. Epithelial Tissue

Structure and Function

Epithelial tissue covers surfaces, lines cavities, and forms glands. It is composed of tightly packed cells with minimal extracellular material. Epithelial cells have polarity, with an apical surface (exposed to the exterior or cavity) and a basal surface (attached to underlying connective tissue via a basement membrane).

• Simple epithelium: Single cell layer; specialized for absorption, secretion, and filtration.

• Stratified epithelium: Multiple cell layers; provides protection in areas of abrasion.

Cell shapes include squamous (flat), cuboidal (cube-shaped), and columnar (tall, column-like).

Types of Epithelial Tissue

• Simple Squamous: Single layer of flat cells; found in lungs, blood vessels (for diffusion/filtration).

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• Simple Cuboidal: Single layer of cube-shaped cells; found in kidney tubules, glands (for secretion/absorption).

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• Simple Columnar: Single layer of tall cells; lines digestive tract (for absorption/secretion).

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• Pseudostratified Columnar (with cilia): Appears layered but all cells touch the basement membrane; lines respiratory tract (for secretion, movement of mucus).

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• Transitional Epithelium: Multiple layers; cells change shape when stretched; found in urinary bladder.

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• Stratified Squamous: Many layers of flat cells; found in skin, mouth, esophagus (for protection).

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• Stratified Cuboidal: Two or more layers of cube-shaped cells; found in ducts of sweat glands, mammary glands.

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B. Connective Tissue

Structure and Function

Connective tissue is the most abundant tissue type in the body, providing support, binding, and protection. It consists of cells embedded in an extracellular matrix of fibers and ground substance. The composition and arrangement of these components determine the tissue's properties.

• Loose Connective Tissue: Areolar, adipose, reticular

• Dense Connective Tissue: Regular, irregular, elastic

• Cartilage: Hyaline, elastic, fibrocartilage

• Other: Blood, bone (osseous tissue)

Loose Connective Tissue

• Areolar: Supports and binds other tissues; found under epithelia.

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• Adipose: Stores fat; insulates and protects organs.

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• Reticular: Forms a soft internal skeleton for lymphoid organs.

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Dense Connective Tissue

• Dense Irregular: Collagen fibers in multiple directions; found in dermis.

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• Dense Regular: Collagen fibers aligned; found in tendons and ligaments.

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• Elastic: Contains elastic fibers; found in ligaments and arteries.

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Cartilage

• Hyaline: Most common; supports and reinforces; found in nose, trachea, ends of long bones.

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• Elastic: Flexible; found in ear, epiglottis.

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• Fibrocartilage: Strongest; resists compression; found in intervertebral discs, pubic symphysis.

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Other Connective Tissues

• Blood: Cells suspended in plasma; transports gases, nutrients, wastes.

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• Osseous (Bone) Tissue: Supports, protects, stores minerals; compact and spongy types.

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C. Muscular Tissue

Types and Functions

Muscular tissue is specialized for contraction and movement. There are three types:

• Skeletal Muscle: Voluntary, striated, multinucleated; attached to bones for movement.

• Cardiac Muscle: Involuntary, striated, branched; found only in the heart.

• Smooth Muscle: Involuntary, non-striated, spindle-shaped; found in walls of hollow organs.

Microscopic Structure

• Skeletal muscle fibers are organized into bundles called fascicles. Each fiber contains myofibrils responsible for contraction.

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• Cardiac muscle cells are branched and connected by intercalated discs for synchronized contraction.

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• Smooth muscle cells are spindle-shaped with a single nucleus; found in the digestive tract, blood vessels, etc.

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D. Nervous Tissue

Structure and Function

Nervous tissue is specialized for communication via electrical impulses. It consists of two main cell types: neurons (transmit signals) and neuroglia (support and protect neurons). The nervous system is divided into the central nervous system (CNS) and peripheral nervous system (PNS).

• Neurons: Large cells with dendrites (receive signals), a cell body, and an axon (transmits signals).

• Neuroglia: Smaller supporting cells; maintain homeostasis, form myelin, and provide support and protection.

Laboratory 9: Comparative Vertebrate Anatomy – External

Introduction

Comparative vertebrate anatomy examines the similarities and differences in the external and internal structures of vertebrates. This field provides insight into evolutionary relationships and adaptations to different environments.

Objectives

• Examine the external anatomy of four vertebrate animals: shark, frog, turtle, and rat.

• Identify major anatomical features and compare adaptations among these species.

Vertebrate Fish – Dogfish Shark (Squalus acanthias)

The dogfish shark is a cartilaginous fish with adaptations for aquatic life, including fins, gill slits, and placoid scales. External features include the mouth, nostrils, eyes, gill slits, fins, and lateral line system.

Vertebrate Amphibian – Bullfrog (Rana catesbeiana)

Bullfrogs are amphibians with moist skin, webbed feet, and adaptations for both aquatic and terrestrial environments. Key external features include the head, trunk, limbs, tympanic membrane, and cloacal opening.

Vertebrate Reptile – Slider Turtle (Trachemys scripta)

The slider turtle is a freshwater reptile with a hard shell (carapace and plastron), scaly skin, and limbs adapted for swimming and walking. External features include the beak, limbs, claws, and tail.

Review Questions and Comparative Tables

• Review questions test understanding of tissue types, their functions, and anatomical adaptations in vertebrates.

Muscle Type	Nuclei	Striated	Cell Shape	Control	Location
Skeletal	Multi	Yes	Long, cylindrical	Voluntary	Attached to bones
Cardiac	1-2	Yes	Branched	Involuntary	Heart
Smooth	1	No	Spindle-shaped	Involuntary	Walls of hollow organs

Example: Blood is classified as a connective tissue because its cells are suspended in plasma, a liquid matrix, allowing for transport of substances throughout the body.