1 Week : Chapter 1 + 5

Chapter 1: Introduction to Anatomy & Physiology
Learn the difference between anatomy and physiology, practise describing locations on an animal’s body, and explore body cavities, levels of organization, and homeostasis.

Chapter 5: Tissues
Explore the four main tissue types: epithelial, connective, muscle, and nervous tissue. We’ll examine how their structures relate to their functions, as well as glands, body membranes, inflammation, and tissue healing.

Learning Objectives:

Explain the difference between anatomy and physiology.
Use anatomical planes, directional terms, and common regional terms to describe the animal body.
Identify the major body cavities and describe their contents.
Describe how cells, tissues, organs, and systems work together.
Explain homeostasis using an animal-related example.
Compare the four main tissue types and their functions.
Describe the roles of glands and body membranes.
Outline the basic processes of tissue healing and repair.

Introduction to Anatomy & Physiology

This chapter establishes the vocabulary and organizational principles used to describe the bodies of domestic animals.

Anatomy and Physiology

Anatomy is the study of body form and structure, while physiology studies how body parts function. Anatomy can be examined at different scales: microscopic anatomy focuses on cells and tissues, whereas macroscopic anatomy examines visible structures such as organs, muscles, and bones.

Ways to Study Anatomy

Regional anatomy studies all structures within one body area. Systemic anatomy studies one body system at a time, such as the skeletal or digestive system. These approaches provide complementary ways to understand the body.

Anatomical Planes and Directional Terms

Reference planes describe how the body can be divided: sagittal planes run lengthwise, the median plane divides the body into equal left and right halves, transverse planes run crosswise, and the dorsal plane divides the body crosswise into equal parts.

Directional terms identify the location of structures precisely. For example, cranial means toward the head, caudal toward the tail, dorsal toward the back, and ventral toward the belly. Medial means toward the midline, while lateral means away from it. On limbs, proximal is nearer the body and distal is farther away. Below the carpus or tarsus, the back of the forelimb is palmar, the back of the hindlimb is plantar, and the front surface is dorsal.

Common Animal Regions

The chapter introduces common external regional terms, particularly for horses. Examples include the withers above the scapulae, the poll between the ears, the barrel of the trunk, the flank along the side of the abdomen, the hock at the tarsus, and the stifle, which corresponds to the human knee region.

Body Cavities

Animals have bilateral symmetry and two main body cavities. The smaller dorsal body cavity contains the central nervous system, including the cranial and spinal cavities. The larger ventral body cavity contains most internal organs and is divided by the diaphragm into the thoracic cavity in front and the abdominal cavity behind.

The thoracic organs are associated with the pleura, while abdominal organs are associated with the peritoneum. In each case, the visceral layer covers the organs and the parietal layer lines the cavity wall.

Characteristics of Living Things

Living organisms share seven key characteristics: movement, respiration, sensitivity, growth, reproduction, excretion, and nutrition. The mnemonic “MRS GREN” helps recall this list.

Levels of Body Organization

The body is organized from simplest to most complex: cells → tissues → organs → systems. Cells are the basic functional units; tissues are groups of specialized cells; organs combine tissues for a shared purpose; and systems are groups of organs working together.

Four Basic Tissue Types

The four major tissue types are:

Epithelial tissue: forms linings, coverings, and glands.

Connective tissue: supports and connects body structures.

Muscle tissue: produces movement; it includes skeletal, smooth, and cardiac muscle.

Nervous tissue: transmits information and controls body functions.

Body Systems and Homeostasis

The body contains 11 major systems, including the: integumentary, skeletal, muscular, digestive, cardiovascular, respiratory, urinary, lymphatic, endocrine, reproductive, and nervous systems.

Tissue Basics:

Histology is the microscopic study of tissues and organs. Tissues are groups of cells working together for a shared function; the four main types are epithelial, connective, muscle, and nervous tissue.

Epithelial Tissue: Covering, Lining, and Secretion

Epithelial tissue covers body surfaces and lines internal spaces. Its roles include protection, filtration, absorption, sensory input, and production of secretions or excretions. Cells are tightly packed, polarized, avascular, and usually innervated.

Epithelia are classified by cell shape (squamous, cuboidal, columnar), number of layers, and surface features such as microvilli, cilia, or keratin. Examples include simple squamous tissue for gas or fluid exchange, simple columnar tissue in the GI tract, and transitional tissue in structures that stretch and contract.

Glands: Specialized Secretory Epithelium

Glands are cells or groups of cells that make and release secretions. Exocrine glands use ducts to release products locally, while endocrine glands lack ducts and release hormones throughout the body. Secretions may be watery (serous) or thick and viscous (mucous).

Connective Tissue: Support, Storage, and Transport

Connective tissue is the most abundant tissue by weight and forms structural and metabolic links among other tissues. It supports and protects organs, stores energy, insulates the body, transports materials, and contributes to healing and defense.

Loose connective tissue: Areolar tissue supports and nourishes; adipose tissue stores energy and provides insulation; reticular tissue forms organ frameworks.
Dense connective tissue: Dense regular tissue forms tendons and ligaments; dense irregular tissue strengthens dermis and organ coverings; elastic tissue permits stretching in structures such as arteries and the bladder.
Specialized connective tissue: Cartilage provides tough, flexible support; bone protects organs, stores calcium, and contains marrow; blood is vascular connective tissue with plasma as its matrix.

Body Membranes: Protective Tissue Layers

Membranes combine epithelial and connective tissues to line cavities, cover surfaces, and separate organs.

Mucous membranes: Monitor material entering the body, produce mucus, and may absorb nutrients.
Serous membranes: Line body walls and cover organs; their parietal and visceral layers produce lubricating fluid.
Cutaneous membrane: The skin, which forms the body’s external covering.
Synovial membranes: Line joint cavities, reduce friction, and produce synovial fluid.

Muscle Tissue: Movement Through Contraction

Muscle fibers contain actin and myosin, proteins that allow contraction.

Skeletal muscle: Voluntary, striated muscle responsible for movement.
Smooth muscle: Involuntary, nonstriated muscle in hollow organs; it drives peristalsis and helps control vessel diameter and bladder emptying.
Cardiac muscle: Involuntary, striated tissue found only in the heart; cells connect through intercalated discs and include pacemaker cells.

Nervous Tissue: Communication and Control

Nervous tissue receives and transmits electrical and chemical signals in the brain, spinal cord, and peripheral nerves. Neurons receive signals through dendrites and send impulses through axons. Neuroglial cells do not transmit impulses but support neurons.

Tissue Healing and Repair

Healing proceeds through injury, inflammation, organization, and regeneration. Inflammation limits damage through vasoconstriction, vasodilation, edema, clotting, phagocytosis, and the release of histamine and heparin. Organization produces granulation tissue, while regeneration involves epithelial coverage and formation of fibrous scar tissue.

Wound-Healing Patterns

First intention: Clean wound with little tissue loss; edges are close together and sutured.
Second intention: Greater tissue loss or separated edges; the wound remains open and heals through granulation.
Third intention: Delayed closure of an older or contaminated wound that was initially left open.

Overall, tissues provide the body’s protective coverings, structural support, movement, communication, transport, and repair capacity.

PP1: Chapter 5 - Summary

Overview

Histology is the microscopic study of tissues and organs.

The body has four primary tissue types: epithelial, connective, muscle, and nervous tissue.

These tissues combine in different ways to form organs.

Epithelial Tissue

Epithelial tissue covers surfaces, lines cavities and organs, and forms glands.

Its functions include protection, filtration, absorption, sensory input, and secretion or excretion.

Key features: cells are polarized with apical and basal surfaces, tightly connected laterally, avascular, and usually innervated.

Classification: based on cell shape (squamous, cuboidal, columnar), number of layers, and surface specializations.

Specializations: microvilli support absorption; cilia move material; keratin creates a protective waterproof barrier.

Major types:

Simple squamous: thin exchange surface for gases or fluids.
Simple cuboidal: secretion and absorption in sheltered areas.
Simple columnar: absorption and secretion in the gastrointestinal tract.
Pseudostratified columnar: commonly ciliated; found in respiratory and parts of the male reproductive tract.
Stratified squamous: protects against mechanical and chemical stress.
Stratified cuboidal: lines large ducts of sweat, mammary, and salivary glands.
Transitional: leak-proof tissue that expands and contracts.

Glands

Glands are single cells or groups of cells that produce and release secretions.

Exocrine glands use ducts to release secretions locally.

Endocrine glands lack ducts and release hormones for distribution throughout the body.

Secretions may be serous (watery) or mucous (thick and viscous).

Connective Tissue

Connective tissue is the most abundant tissue by weight.

It connects, supports, protects, insulates, stores energy, transports substances, and contributes to healing and immune defense.

Loose connective tissue:

Areolar: surrounds and supports tissues and provides nutrients.
Adipose: stores energy, insulates, and absorbs shock.
Reticular: forms supportive frameworks, or stroma, in organs such as the liver, spleen, lymph nodes, and bone marrow.

Dense connective tissue:

Dense regular: parallel collagen fibers in tendons, ligaments, fascia, and muscle coverings.
Dense irregular: randomly arranged collagen in the dermis, organ coverings, and joint capsules.
Elastic: stretchable tissue in arteries, airways, bladder, stomach, heart regions, and certain ligaments.

Supportive connective tissue:

Cartilage: tough, avascular, and non-innervated.
Hyaline is rigid, elastic is flexible, and fibrocartilage resists compression.
Bone: hard, vascular tissue that protects organs, stores calcium, and contains bone marrow.
Vascular connective tissue: blood, whose matrix is plasma.

Body Membranes

Membranes combine epithelial and connective tissue to line cavities, cover surfaces, and separate organs.

Mucous membranes: line passages that connect to the exterior; often produce mucus and may absorb nutrients.
Serous membranes: line body walls and cover organs.

Their parietal layer lines cavities, while the visceral layer covers organs.

Cutaneous membrane: the skin or integument.
Synovial membranes: line joint cavities, reduce friction, and produce synovial fluid.

Muscle Tissue

Muscle fibers use actin and myosin to contract.

Skeletal muscle: voluntary, striated tissue responsible for movement.
Smooth muscle: involuntary, nonstriated tissue in hollow organs; supports peristalsis, vessel constriction, and bladder emptying.
Cardiac muscle: involuntary, striated tissue found only in the heart; cells connect through intercalated discs and include pacemaker cells.

Nervous Tissue

Nervous tissue receives and transmits electrical and chemical signals in the brain, spinal cord, and peripheral nerves.

Neurons receive signals through dendrites and carry impulses away through axons.

Neuroglial cells are more numerous than neurons and provide support but do not transmit impulses.

Tissue Healing and Repair

Healing progresses through injury, inflammation, organization, and regeneration.

Inflammation: isolates damage and limits further injury.

It includes vasoconstriction followed by vasodilation, edema, clot formation, phagocytosis, and the dispersal of histamine and heparin.

Organization: granulation tissue develops as repair begins; excessive granulation may form proud flesh.
Regeneration/fibrosis: epithelial tissue covers the wound, the scab is shed, and granulation tissue becomes fibrous scar tissue.

Adhesions may occur.

Wound-Healing Classifications

First intention: clean wound with minimal tissue loss; edges are close together and sutured, ideally within about 6 hours.
Second intention: greater tissue loss or irregular, separated wound edges; the wound remains open.
Third intention: delayed closure after a contaminated or older wound has initially been left open.

The chapter emphasizes how tissue structure determines function, from protective epithelial layers to supportive connective tissues and the coordinated repair of injuries.

P2: Chapter 5 - Tissues Summary

Tissues are groups of specialized cells that work together; their structure determines their role in organs and body systems.

Tissue Organization

Cells → tissues → organs → systems → animal. Histology is the microscopic study of tissues and organ structure.

Four Basic Tissue Types

Epithelial: Covers body surfaces, lines organs and cavities, and forms glands. Its roles include protection, filtration, absorption, sensation, secretion, and excretion.
Connective: Supports, connects, protects, insulates, stores energy, and transports substances. Examples include fat, tendons, ligaments, cartilage, bone, and blood.
Muscle: Contracts to produce movement. Skeletal muscle moves the body, smooth muscle moves materials through hollow organs, and cardiac muscle pumps blood.
Nervous: Communicates and controls body functions through electrical and chemical signals. It is found in the brain, spinal cord, and peripheral nerves.

Epithelial Tissue Classification

Epithelia are classified by cell shape, number of layers, and surface specialization.

Shapes: Squamous (flat), cuboidal (cube-shaped), and columnar (tall).
Layers: Simple (one layer), stratified (two or more), and pseudostratified (appears layered but all cells touch the basement membrane).
Specializations: Microvilli increase absorption; cilia move material; keratin provides a tough, waterproof protective barrier.

Glands

Glands produce and release secretions.

Exocrine glands: Have ducts and release secretions onto surfaces or into local areas, such as salivary, sweat, and sebaceous glands.
Endocrine glands: Are ductless and release hormones into blood or interstitial fluid, such as the thyroid, adrenal, and pituitary glands.

Connective Tissue Groups

Connective tissue proper: Loose tissue binds and fills spaces; dense tissue provides strong attachments. Tendons connect muscle to bone, while ligaments connect bone to bone.
Supportive connective tissue: Cartilage provides flexible support and heals slowly because it lacks blood vessels. Bone is rigid, well vascularized, stores minerals, and houses marrow.
Vascular connective tissue: Blood has plasma as its extracellular matrix and transports gases, nutrients, wastes, and other substances.

Body Membranes

Mucous membranes: Line passages open to the outside, including digestive and respiratory tracts; they protect, secrete, and may absorb.
Serous membranes: Line closed body cavities and cover organs, reducing friction through a small amount of fluid.
Cutaneous membrane: The skin; it covers the body and acts as a protective barrier.
Synovial membrane: Lines joint cavities and produces lubricating synovial fluid.

Tissue Healing

Healing occurs in four broad phases: injury → inflammation → organization → regeneration.

Inflammation: Blood-vessel changes, swelling, clotting, and white blood cell activity limit damage and remove debris.
Organization: New capillaries grow, fibroblasts make collagen, and granulation tissue forms.
Regeneration: Epithelial cells cover the wound; the wound contracts and may form collagen-rich scar tissue.

Key Idea

Epithelial tissue covers and lines, connective tissue supports and connects, muscle tissue moves, and nervous tissue communicates and controls.