Membranes and Tissues

Levels of Organization

Organelles - > Cell - > Tissue - > Organ - > Organ System - > Organism

Tissue

any group of cells performing the same function

Histology

the study of tissues

4 types of tissue

1. Epithelial

2. Connective

3. Muscular

4. Nervous

Epithelial (Function)

covers body surfaces and lines cavity

Connective (Function)

binds and supports body parts

Muscular (Function)

muscle contractions

Nervous

responds to stimuli and transmits impulses

Differences between the Tissues Include:

1. Structure of the cell

2. Matrix or substance that surrounds the tissue

3. Nature and function of the fibers that make up tissues

Epithelial Tissue

• Forms continuous layers over the entire body surface and body’s inner cavities (tightly packer cells with very little space)

• Protects body and prevents it from drying out (especially skin)

• May absorb or secrete materials

• High ability for regeneration

• May have microvilli or cilia

All the Functions of Epithelial Tissue

1. Protection

2. Absorption

3. Transport

4. Filtration

5. Gas exchange

6. Secretion

Protection

can form thick layers of protection (underneath the portion of the skin)

Absorption

microvilli - absorb materials

Transport

some have cilia to move small particles

Filtration

Kidney cells

Gas Exchange

lining of the lungs (oxygen and carbon dioxide)

Secretion

lining of the mouth secretes saliva, glands secrete sweat, and digestive juices

3 Types of Epithelial Tissue - Classified by Shape

1. Squamous

2. Cuboidal

3. Columnar

Squamous

a) flat cells

b) lining of lungs and blood vessels

For transfers!

Cuboidal

a) cube shaped

b) Lining kidney tubules

For protection!

Columnar

a) pillar or column shaped

b) lining of digestive tract

For protection!

3 types of Epithelial Tissue - Classified by Layers

1. Simple

2. Stratified

3. Psuedostratified

Simple

Single layer

Stratified

multiple layer

Pseudostratified

Single layer that appears multiple, but each cell touches the surface

Glandular Epithelium Tissue

• Tissue secretes a product

• Can be a single cell or many cells

• 2 types

  • Endocrine

  • Exocrine

Endocrine

Secretes directly into the blood stream

• Pituitary and Thyroid glands

Exocrine

Secretes into ducts

• Salivary and Sweat gland

Simple Squamous (Locations)

• Walls of capillaries

• Lining of blood vessels

• Air sacs of lungs

Simple Squamous (Function)

• Filtration

• Diffusion/Osmosis

Simple Cuboidal (Locations)

• Surface of ducts of glands

• Lining of kidney tubules

Simple Cuboidal (Functions)

• Secretion

• Absorption

Simple Columnar (Locations)

• Lining of uterus

• Tubes of digestive tract

Simple Columnar (Functions)

• Protection

• Secretion

• Absorption

Stratified Squamous (Locations)

• Lining of esophagus, mouth, vagina, epidermis

Stratified Squamous (Functions)

• Protection from abrasion and desication in Keratinized form

Stratified Cuboidal

• Not common

• Mostly found in larger ducts of certain glands like the mammary and salivary glands

• Usually only has 2 layers

Pseudostratifed Cililated Columnar (Location)

• Lining of reproductive system tubes and respiratory passages

Pseudostratifed Cililated Columnar (Function)

• Appears stratified but each cell touches the basement layer

• Have cilia - movement of mucus and sex cells

• Column shape

• Protection

Transitional Epithelium

• Line walls of the urinary bladder, ureter, and urethra ( need to stretch)

• When walls are relaxed consist of several layers of cuboidal cells

• When walls are stretched/distended outer cell stake on a squamous appearance (cells can slide past each other)

Connective Tissue

• Most widespread and diverse type of tissue

• Most are heavily vascularized (lots of blood in them)

Types of Connective Tissue

a. Fibrous Connective Tissue

b. Cartilage

c. Bone

d. Blood

Types of Fibrous Connective Tissue

1. Loose/Areolar Tissue

2. Adipose Tissue

3. Dense Tissue

Types of Cartilage

1. Hyaline Tissue

2. Elastic Tissue

3. Fibrocartilage Tissue

Types of Bone

1. Compact

2. Spongey

Connective Tissue Functions

1. Binds structures together (tendons connect to bones)

2. Provides support and protection

3. Fills space

4. Produces blood

5. Stores fat (energy and help maintain homeostasis)

   • Consists of cells separated by a non-cellular matrix

   • Matrix varies in consistency from solid to fluid

Matrix Combinations

• Properties are derived from the characteristics of the matrix

• White Fibers

• Yellow Fibers

• Reticular Fibers

White Fibers

collagen (bundles) that give flexibility and strength

Yellow Fibers

elastin that is not as strong as collagen but is able to stretch

Reticular Fibers

very thick and highly branched colllagenous fibers that form a network

Types of Matrix

• Fibrous

• Gel-like

• Hard

• Liquid

Fibrous (Description)

Loaded with protein fibers like collagen

Fibrous (Example)

Scab and scar formation

Gel-like (Description)

Soft and Flexible

Gel-like (Example)

Breast tissue

Hard (Example)

Bone

Liquid (Example)

Blood

Loose (Areolar) Connective Tissue (Location)

• Between muscles

• Beneath the skin

• Beneath most epithelial layers

Loose (Areolar) Connective Tissue (Function)

• Binds structures more specifically organs together

• Cells are fibroblasts that produce fibers

Adipose (Location)

• Beneath the skin

• Around the kidney and heart

• In the breast

Adipose (Function)

• Cells are fibroblasts that enlarge and store fats

• Limited matrix

• Used for insulation

Dense Connective Tissues

• Matrix produced by fibroblasts that contain thick bundles of collagen fibers

• Two types

  • Dense Regular Connective Tissue

  • Dense Irregular Connective Tissue

Dense Regular Connective Tissue

• Bundles are parallel

  • Tendons (muscle to bones)

  • Ligaments (bones to bones)

  • Aponeuroses (muscle to muscle)

Dense Irregular Connective Tissue

• Bundles run in different directions

  • Inner portions of the skin and joint capsules (envelope surrounding a synovial joint)

Reticular Connective Tissue

• Made of fibroblasts

• Matrix contains only reticular fibers

• Forms lymphoid tissue found in the lymph nodes, spleen, thymus, and bone marrow

• Acts as a part of the immune system

Hyaline (Location)

• Ends of bones

• Nose

• Rings in walls of respiratory passages

• Between ribs and sternum

• Makes up the fetal skeleton

Hyaline (Function)

• Most common

• Matrix contains very fine collagenous fibers

• appears glassy, white, and opaque

• Used for protection and support

Elastic

• Matrix has many elastic fibers

• More flexible

• Outer ear

Fibrocartilage

• Matrix has strong collagenous fibers

• Absorbs shocks and reduces friction

• Vertebral discs and knee joints

Bone

• Compact and Spongy

• Most rigid connective tissue

• Extremely hard matrix of mineral salts, primarily calcium

• Deposited around protein fibers

Compact Bone (Location)

• Bones of skeleton

• Composed of osteons or Haversian system (many circular/cylindrical shaped units)

• Osteocytes are located in the lacunae (cavities) that are arranged in lamellae (concentric circles)

Compact Bone (Function)

• In osteons, matrix is composed of lamellar

• Central canals contain blood vessels and nerves which bring blood to osteocytes

Spongy

• Ends of long bones - spongy bone

• Bony bars and plates separated by irregular spaces

• Part of the bone that was red blood cells

Blood

• Cells are separated by plasma

• Cells are called “Formed Elements”

• 3 types of formed elements

  • Erythrocytes

  • Leukocytes

  • Throbocytes

• Plasma is the only matrix not made by the cells of the tissue - it’s produced as different molecules enter the blood at various organs

Erythrocytes

red blood cells that carry oxygen

Leukocytes

white blood cells that fight infections

Thrombocytes

Cell fragments of megakaryocytes (so not a cell) that are platelets that cause blood clotting

Muscular Tissue

• Composed of muscle fibers that contain actin and myosin

• Interaction between the fibers allows cells to contract

3 types of Muscle Tissue

1. Skeletal

2. Smooth

3. Cardiac

Skeletal (Location)

• Attached to the bones of the skeleton

• Multinucleated - nuclei lie just inside of the cell membrane

• Have light and dark bands-striated

Skeletal (Function)

• Under conscious control - voluntary

• Contracts the fastest of all muscles

Smooth Muscle (Location)

• Found in the visceral organs and blood vessels

• Spindle-shaped cells

• Lacks striations

Smooth Muscle (Function)

• Contracts the slowest of all muscles

• Not under voluntary control - involuntary

Cardiac Muscle (Location)

• The heart

• Combination of both striations and under involuntary control

• Muscle fibers are branched and seem to fuse to one another

• Bound end to end intercalated disks (areas of folded plasma membrane)

Nervous Tissue

• Found in the brain, spinal cord, and nerves

• Specialized cells are neurons

• Conduct impulses from and to body parts

• Cause muscles to contract

• Contains neuroglial cells that support and nourish neurons

3 Parts of a Neuron

1. Dendrite

2. Cell Body

3. Axon

Dendrite

receives signals that many result in a nerve impulse

Cell body

contains the nucleus and most of the cytoplasm

Axon

conducts nerve impulses

Neuroglia

• Outnumbers neurons 9 to 1

• Take up more than half the volume in the brain

• supports and nourishes neurons

4 Types of Neuroglia

1. Microglia

2. Astrocytes

3. Oligodendrocytes

4. Ependymal

Microglia

supports neurons; engulf bacteria and cellular debri

Astrocytes

• provide nutrients to neurons and produce a hormone called glia

• glia is a derived growth factor

  • important in potential cures for Parkinson’s Disease

Oligodendrocytes

produce myelin, protective layer of fatty insulation

Ependymal

form a plasma-like solution called cerebrospinal fluid (CSF) which supports and nourishes the brain and spinal cord

5 types of Body Membranes

1. Mucous

2. Serous

3. Synovial

4. Meninges

5. Cutaneous

Muscous (Location)

• Line the interior walls of organs and tubes that open to the outside of the body

• Digestive, respiratory, urinary, and reproductive systems

• Consist of an epithelium and connective tissue layer

Muscous (Function)

• The epithelium contains goblet cells that secrete mucus

• Mucus protects interior walls from invasion of bacteria and virus

• More mucus is secreted during times of illness

• Protects walls of the digestive tract from digestive enzymes

• A breakdown of a membrane is an ulcer

Serous (Location)

• Line cavities including thoracic and abdominopelvic

• covers internal organs

• 2 layers

  • Parietal which covers the wall of cavities

  • Visceral that covers the surface of organs

• Composed of a squamous epithelium and a layer of connective tissue

Serous (Function)

• Secretes serum that is a light-yellow liquid left after all blood clotting factors are removed

  • reduces friction between organs/viscera rubbing together or against the cavity wall