BIO 120 Chapter 4 - Tissues

Tissue

Groups of cells and the surrounding extracellular substances working together to carry out a common function

Histology

The study of tissues

4 primary tissue types

• Epithelial

• Connective

• Muscular

• Nervous

Epithelial

• Covers body surface

• Lines hollow organs and body cavities

• Forms glands

Connective

• Binds organs together

• Stores energy as fat reserves

• Transports protects and supports

Muscular

• Specialized for contraction and generation of force

• Generates heat

Nervous

• Detects changes

• Communicates with nerve impulses to activate muscles or glands

What is the structure of epithelial tissue

Composed of cells that are close together

Avascular

Does not have its own blood supply (epithelial tissue)

Epithelial Tissue - Function

• Protects structures from abrasion

• Acts as barrier

• Permits diffusion of certain substances

• Glands secretion

Squamous

Cell shape

• Thin/ flat

Cuboidal

Cell shape

• Cube like

Columnar

Cell shape

• Longer than it is wide

Simple

1 layer

Pseudostratified

• False stratified

• Actually 1 layer but nuclei appear at different heights

Stratified

Multiple layers

Simple Squamous ET

Structure: 1 layer of thin cells

Function: Creates a minimal barrier which is great for quick diffusion

Location: Areas where substances must easily pass from point A to point B

• Alveoli of lungs

• Inner lining of blood vessels

Simple Cuboidal ET

Structure: 1 layer of cube cells

Function: Absorption and secretion

Location: Lining of glands and tubules

• Renal tubes in kidney

Simple and pseudostratified columnar ET

Structure: 1 layer of tall cells

Function: Absorption, secretion, and transportation

Locations: Digestive tract, respiratory tract, reproductive tract

Microvilli

• Microscopic finger like extensions of the plasma membrane

• Increased surface area of cell

• increase rate of absorption

Cilia

• Microscopic hair like projections

• wave to create movement of fluid outside of the cell

• aids in transportation

Goblet cells

• Single celled glands that secrete mucus

• Serves as lubricant and protection

Stratified Squamous ET

Structure: Multiple layers of flat cells

Function: Protection from abrasion, water loss and pathogens

Locations: Areas of high friction

• skin, mouth, esophagus, anus, vagina

Transitional ET

Structure:

• Low fluid volume/relaxed/ empty bladder= columnar or cuboidal shape

• High fluid volume/stretched/ full bladder= squamous shape

Function: Accommodates stretching without tearing // allows for a fluctuation in the volume of fluid filling space

Desmosomes

• Desmo = bond

• Found between cells

• holds cells together

Hemidesmosome

• Hemi= half

• tiny, stud-like cellular structures that anchor the bottom of epithelial cells to the underlying extracellular matrix or basement membrane

Tight junctions

• prevent leakage between cells

Gap junctions

• a specialized intercellular connection that forms a tunnel-like channel directly linking the cytoplasm of neighboring animal cells

Exocrine glands

• has ducts

• secretes substances onto a body surface or into a body cavity

• Ex- sweat, oil, earwax, mucous, saliva

Endocrine glands

• No ducts

• secretes substances (hormones) directly into bloodstream

Connective tissues

• widely scattered cells within large extracellular matrix

Functions

• enclose organs and separate organs into layers

• connect tissues to one another

• support and movement

• storage

• cushion and insulate

• transport

• protect

Areolar

• Loose connective tissue

• cushion for most organs

• attaches skin to underlying tissues

• loose arrangement of fibers

Adipose

• loose connective tissue

• contains adipocytes

• small amount of extracellular matrix

• heat insulator and energy storage

Dense connective tissue

• collagen fibers tightly packed and running in same directions

• can withstand great pulling force due to tensile strength and stretch resistance

Ligaments

connect bone to bone

Tendons

connect muscle to bone

Specialized connective tissue : cartilage

• hyaline cartilage

• elastic cartilage

• fibrocartilage

Specialized connective tissue : Bone

• compact bone

• spongy bone

Compact bone

• solid no space between layers

• provides bone with strength and rigidity

• forms outer layer of bones

• concentric circles=lamellae

Spongy bone

• spaces between trabeculae

• weighs less than compact bone

• filled with hemopoietic tissue

• interior layer of bone

Specialized connective tissue : Blood

• fluid matrix // lacks protein fibers // RBC, WBC, platelets

• transports gases, wastes, and hormones

• protects body from infection and helps regulate body temp

Muscular tissue

• responsible for movement of and within the body

• has the ability to contract and generate force

Mucous membranes

• moist tissue linings that cover body cavities and internal passageways open to the outside environment

Serous membranes

• a thin, smooth tissue layer that lines closed internal body cavities and covers the organs inside them to reduce friction

Synovial membranes

• a specialized layer of connective tissue that lines the inner cavities of freely movable joints, tendon sheaths, and bursae