TISSUES & STRUCTURES 1

INTRODUCTION

Cellular level e.g. cell: smallest living units in body.

Derived from 3 germ layers.

Tissue level e.g. gastric tissue: groups of cells working together to perform one or two functions.

Organ level e.g. stomach: same type of tissue but functions as independent unit in an integrated system.

System level e.g. Gastrointestinal: collection of organs & structures with a common function.

Organism level e.g. human

Every part of human body made up of one or more main tissue types viz.:-Epithelial-Connective-Muscle-Nervous

EPITHELIAL TISSUE

Covers exposed surfaces, lines internal passageways and chambers and forms glands.

Functions

Provide physical protection

Control permeability

Provide sensation

Produce specialized secretions

Three descriptors:

1) Lining

2) Glandular

LINING EPITHELIUM

Simple (one layer)

-Squamous

-Cuboidal

-Columnar

-Pseudostratified

Two types: Simple, Stratified

Stratified (many layers)-Squamous

-Transitional

SIMPLE SQUAMOUS

Shape: thin, flat and irregular; like jigsaw puzzles

Most delicate type

Located in regions where absorption or diffusion takes place or in slippery places e.g. Body cavity.

Function: reduce friction, control vessel permeability, perform absorption and secretion.

lines ventral body cavities (mesothelium); heart & bld vsls(endothelium), nephrons of kidney, inner lining of cornea, alveoli in lungs.

SIMPLE CUBOIDAL

Shape: resemble hexagonal boxes, have nuclei at center

Function: limited protection, absorption and secretion.

lines glands, ducts, portions of kidney tubules, thyroid gland.

Structures:

Cell membrane

Nucleus

cytoplasm

SIMPLE COLUMNAR

Shape: rectangular, hexagonal, taller, more slender.

Elongated nuclei close to basal lamina

Located in regions where absorption or secretion occurs e.g. small

intestine.

In stomach & large intestine, protects from chemical stresses.

Function: protection, absorption and secretion.

lines stomach, intestine, gallbladder, uterine tubes and collecting ducts of kidneys. Structures:

Surface of tissue

Mucus

Goblet cells

Nucleus

PSEUDOSTRATIFIED COLUMNAR

Has several types of cells with varying shapes and functions.

Not truly stratified because every cell contacts the basal lamina.

Possess cilia

lines nasal cavity, trachea, bronchi, portions of male repr. Tract.

Function: protection and secretion.

Structures

Cilia

Surface of tissue

Goblet cells

Nuclei

STRATIFIED SQUAMOUS

Has keratin (protein) is exposed areas to dehydration

Non-keratinized resists abrasion.

Located where mechanical stresses are severe e.g. esophagus.

Located in surface of skin (keratinized), lining of mouth, throat,

esophagus, rectum, anus and vagina.

Function: physical protection.

Structures

Surface

Squamous cells

Reproducing cells

STRATIFIED CUBOIDAL

Rare

Located along ducts of sweat glands and in larger ducts of mammary

glands.

Function: protection, absorption and secretion.

lines some ducts. Similar to simple type but with more layers

STRATIFIED COLUMNAR

Relatively rare

Has either two or multiple layers.

Located in small areas of pharynx, epiglottis, anus, mammary gland, salivary gland ducts, and urethra.

Function: protection

TRANSITIONAL

Tolerates repeated cycles of stretching and recoiling without

damage

Appearance changes with stretching

Located urinary bladder, renal pelvis of kidneys, ureters.

Function: permits expansion and recoil.

GLANDULAR EPITHELIUM

Endocrine

Release secretions to interstitial fluid (bloodstream).

Secretions called hormones

Ductless glands

Examples: thyroid, pituitary, pancreas, thymus.

Exocrine

Release secretions into ducts

Enzymes entering GIT, skin, tears and mammary glands.

Common mode of secretion: merocrine (mucin-mucus).

ENDOCRINE GLANDS

EXOCRINE GLANDS

CLASSIFICATION

Modes of secretion

Merocrine Apocrine Holocrine

Types of secretions

Serous (parotid) Mucous (sublingual) Mixed (submandibular)

Structure

-unicellular (goblet cells)

-& multicellular

Structure: simple & compound Shape (tubular: straight or coiled; alveolar)Simple:

Tubular straight in intestinal glands

Tubular coiled in sweat glands

Alveolar: sebacious glands

Compound: tubular (mucous gl. Mouth), testes

Alveolar: mammary gl., salivary, pancreas.

EXOCRINE GLANDS..secretions

Release from vesicle

Loss of cytoplasm

Destroys gland cell

EXOCRINE GLANDS..structure

CONNECTIVE TISSUE

Connective tissue proper

Loose areolar

Adipose

Dense regular

Dense irregular

*Also called collagenous tissue (rich in collagen fibers)

Supporting connective tissue

Fibrous

Hyaline cartilage

Elastic cartilage

Fibrocartilage

LOOSE AREOLAR

Separates skin from deep structures, loosely organized fibers (superficial fascia) Absorbs shock

Has elastic fibers hence returns to shape Has capillaries for 02 and nutrients

Surround and support blood vessels and nerves

Structures:

Ground substance

Fibroblast

Collagenous fiber

Elastic fiber

ADIPOSE TISSUE

Located deep to skin esp. at sides, buttocks, breasts, padding around eyes and kidneys.

Function: provides padding and cushions shock, insulates (reduces heat loss); stores energy.

Either white (yellowish) or brown in colour

RETICULAR TISSUE

Location: Liver, kidney, spleen, lymph nodes and bone marrow.

Functions: Provides supporting framework.

Reticular fibers (black)

DENSE REGULAR TISSUE

Located tendons & aponeurosis, ligaments, covering skeletal muscle as deep fascia.

Functions: provides firm attachment, conducts pull of muscle, reduces friction, stabilizes relative positions of bones.

Collagen fibers

Fibroblast nuclei

DENSE IRREGULAR

Located on capsules of visceral organs, periostia and periochondria, nerve and muscle sheaths, dermis.

Functions: provides resistance to forces from different sides, prevents overexpansion such as bladder.

Collagen fiber bundles

ELASTIC TISSUE

Located in ligamentum flavum and nuchae, ligaments supporting penis, ligaments supporting transitional epithelium, blood vessel walls.

Functions: stabilizes positions of vertebrae and penis, cushions shocks, permits expansion and contraction

Elastic fibers

Fibroblast nuclei

FLUID CONNECTIVE TISSUE.blood tissue

Red Blood Cells (RBCs)

Platelets

Tiny pockets

of cytoplasm

WHITE BLOOD CELLS (WBCs)

For immune system (protection from infection and disease)

Monocyte

Lymphocytes

Eosinophil

Neutrophil

Basophil

SUPPORTING CONNECTIVE TISSUEcartilage

Matrix is firm gel containing polysaccharides

Cartilage cells called chondrocytes occupying lacunae

Separated from other structures by perichondrium

TYPES

HYALINE

ELASTIC

FIBROCARTILAGE

HYALINE CARTILAGE

Location: between tips of ribs and bones of sternum e.g. costal cartilage, bone surfaces of synovial joints, supports larynx, trachea and bronchi, form

part of nasal septum.

Function: provides stiff, flexible support; reduces friction.

Chondrocyte in lacuna

Nucleus

Ground substance

ELASTIC CARTILAGE

Located in auricle of external ear, epiglottis, auditory tube, cuneiform cartilages of larynx.

Functions: provides support, tolerate distortion without damage & returns to original shape.

Similar to hyaline except abundant

elastic fibers

FIBROCARTILAGE

Located in menisci, pubic symphysis, intervertebral discs.

Functions: Resists compression, prevents bone to bone contact, limits relative movement.

Chondrocytes in lacuna

Collagen fibers

NERVOUS TISSUE

A) Neurons

MYELIN

produced by Oligodendrocytes in CNS and Schwann cells in PNS

Functions in enhancing conduction rates.

NEUROGLIA

Protoplasmic astrocytes (in dendrites and cell bodies of CNS) [Gray matter]

Fibrous astrocytes (in myelinated axons) [white matter)

B) Connective tissue

MUSCLE TISSUE

Skeletal

Smooth

Cardiac

SKELETAL MUSCLE

Cells are long, cylindrical, striated and multinucleate. Voluntary

Located in skeletal muscles with connective and neural tissue. Function: Moves or stabilizes position, guards entrances and exits to digestive,

respiratory, and urinary tracts, generates heat, protects internal organs.

Parallel muscle fibers

Striations

Nuclei

CARDIAC MUSCLE

Cells are short, branches, striated, usually with a single nucleus, cells are interconnected by intercalated discs.

Involuntary

Location: Heart

Function: Circulates blood, maintains blood pressure.

Cardiac muscle cellsNucleusStriationsIntercalated discs (black)

SMOOTH MUSCLE

Cells are short, spindle-shaped, non-striated with a single nucleus.

Involuntary

Location: walls of blood vessels and in digestive, respiratory, urinary and reproductive organs.

Smooth muscles cellNucleus

BONE TISSUE

Has small ground substance

2/3rds have mixture of calcium salts (primarily calcium phosphate), rest by collagen fibers.

Canaliculi

Osteocytes in lacuna

Haversian canals

TISSUES & STRUCTURES 2

SYSTEMS

SYSTEMATIC ANATOMY

The Integumentary System

The Skeletal System

The Nervous System

The Muscular System

The Cardiovascular System

The Respiratory System

The Gastrointestinal System

The Urogenital System

The Endocrine System

The Immune/Lymphoid System

INTEGUMENTARY

Protects against environmental hazards, helps control body temperature

SKELETAL SYSTEM

Provides support, protects tissues, stores minerals, forms blood.

MUSCULAR SYSTEM

Produces movement and locomotion; provides support; generates heat.

NERVOUS SYSTEM

Directs immediate response to stimuli, usually by coordinating the activities of other organ systems.

ENDOCRINE SYSTEM

Directs long-term changes in other organ systems.

CARDIOVASCULAR SYSTEM

Transports cells and dissolved materials including nutrients, wastes and gases.

LYMPHOID SYSTEM

Defends against infection and disease; returns tissue fluid to bloodstream

RESPIRATORY SYSTEM

Delivers air to sites where gaseous exchange can occur between air and circulating blood.

DIGESTIVE SYSTEM

Processes food, absorbs nutrients, eliminates waste products.

URINARY SYSTEM

Eliminates excess water, salts, and waste products.

FEMALE REPRODUCTIVE SYSTEM

Produces sex cells and hormones.

MALE REPRODUCTIVE SYSTEM

Produces sex cells and hormones