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Tissue

• A tissue is a group of similar cells, that function together to carry out specialised activities

There are four types1. Epithelial tissue2. Connective tissue3. Muscular tissue4. Nervous tissue

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Epithelial Tissue

• Makes up 3% of your body weight• They don’t move• They don’t send messages• Their cells are all touching one another• Of all tissues, they are the most widely varied

in structure and function

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Locations of Epithelial Tissues

• Covers the body (epidermis)• Found on the inside of hollow organs and the

outside of all organs• Found above a connective tissue layer (epi =

above)• Lines the cavities, tubes, ducts, and blood

vessels inside the body

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Epithelial Anatomy• Apical surface – upper surface that is free or exposed

to the “exterior”• Basal surface – attached surface (below)• Microvilli – small fingerlike extensions that increase

the surface area allowing for more work to be done

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Functions of Epithelial Tissue– Protects from physical & chemical injury– Protects against microbial infection– Contains nerve endings which respond to

stimuli– Filters, secretes & reabsorbs materials– Secretes fluids to lubricate joints

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Types of Epithelial Membranes

• Mucous or mucosa– lining of tubes; moistens and protects from enzymes (stomach, trachea, and vagina)

• Serous or serosa – outside of organs; lubricates (all thoracic, abdominal and pelvic organs)

• Cutaneous or skin – body surface; protection

• Synovial – synovial joints; lines and protects synovial cavities (elbow, knee, hip, etc.)

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General Features of Epithelial Tissue

1. The cells are arranged in continuous sheets single or continuous layers.2. Have an apical surface exposed to a body cavity, lining of an internal organ or the exterior of the body; lateral surface facing adjacent cells on either side, basal surface which are the deepest layers of the cell3. Lack blood vessels get nutrients by diffusion.4. They have a nerve supply.5. They have a high capacity for renewal by cell division.

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Arrangement of cells in layers

Simple epithelium• Is a single layer of cells that functions in

diffusion, osmosis, filtration, secretion and absorption.

• Secretion is the production and release of mucus, sweat or enzymes.

• Absorption is the intake of fluids or other substances such as digested food from the intestinal tract

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Arrangement of cells in layers Stratified epithelium (stratum = layer)

• Consists of two or more layers of cells that protect underlying tissues in locations where there is considerable wear and tear

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Three Basic Shapes• Squamous – like scales, or

pancakes (“being squashed like a pancake”)

• Cuboidal – looks like cubes

• Columnar – longer and look like columns

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Squamous Epithelium

• Simple – one cell thick

• Forms solid layer of cells which line blood vessels, body cavities and covers organs in body cavities

• Stratified – multiple layers• Forms epidermis

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Simple Squamous Epithelium

• Found in parts of the body where filtration (kidneys) or diffusion (lungs) are priority processes.

• Simple squamous epithelium that lines the heart & blood vessels is known as endothelium.

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Simple Squamous

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Simple cuboidal epithelium

• Found in organs such as the thyroid gland and kidneys.

• Performs the functions of secretion and absorption.

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Cuboidal Epithelium

• Simple – one cell thick

• Roughly cube shaped

• Line ducts in kidneys where re-absorption and secretion activities take place.

Duct

Cuboid Cells

Duct

Cuboid Cells

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Simple Cuboidal

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Columnar Epithelium

• Simple – one cell thick

• Column shaped (long and narrow)

• Lines digestive tract where re-absorption & secretion occurs.

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Simple columnar epithelium

• There are ciliated and non ciliated

Non ciliated:• Those with microvilli increase the surface area of the

plasma membrane. =increasing the rate of absorption of the cell.

• Goblet cells secret mucus• Mucus serves as a lubricant for the lining of the digestive

and respiratory tract.• It helps trap dust entering the respiratory tract.• Prevents destruction of the stomach lining by acid secreted

by the stomach.

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Nonciliated Simple Columnar

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Simple columnar epithelium Ciliated simple columnar epithelium

• Contain cells with cilia at their apical surface.• In some parts of the upper respiratory tract

mucus secreted by the goblet cells forms a film over the respiratory surface that traps inhaled foreign particles.

• The cilia move the foreign particles towards the throat where it can be coughed up swallowed or spit out.

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Ciliated Simple Columnar

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Stratified epithelium

Stratified squamous epithelium

• Cells in the apical layer are flat.• The basal (deepest) cells continuously

undergo cell division.• The cells are pushed upwards towards the

surface.• At the apical layer the cells die replaced by

cells emerging from the basal cells.

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Stratified Squamous Epithelium

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Connective Tissue• Protects and supports the body and its organs

together, stores energy reserves as fat & provides immunity

Examples: • Cartilage• Bone tissue• Liquid connective tissue (blood tissue)• Adipose tissue

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Connective Tissue

• Binds together, supports and strengthens other body tissues

• Protects and insulates internal organs• Compartmentalizes structures such as skeletal

muscle• The major transport system within the body• Site of stored energy reserves• Main site of immune responses

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General Features of Connective Tissue• 2 basic parts:

– Cells and Matrix

• Matrix – material between widely spaced cells– Consists of protein fibers and ground substance

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General Features of Connective Tissue

• Does not occur on free surfaces• Has a nerve supply (except cartilage)• Highly Vascular (except cartilage and tendons)

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Connective Tissue

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Adipose tissue

• Has cells called adipocytes.• They are specialised for the storage of

triglycerides (fats).• Adipose tissue is a good insulator and can

reduce heat loss through the skin.

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Adipose tissue

• It is a major energy source.• It protects various organs.• As the amount of adipose tissue increases

with weight gain new blood vessels form.• Thus an obese person has more blood vessels

than a lean person.• A situation that can cause high blood pressure

since the heart has to work harder.

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Adipose Tissue

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Connective Tissue Matrix – Fibers

• Strengthens and supports connective tissue

– Collagen Fibers• Strong, resist pulling forces, flexible• Made of the protein collagen which is the most

abundant protein in your body

– Elastic Fibers• Smaller in diameter than collagen fibers, branch to

form network• Made of the protein elastin

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Muscular Tissue

• Generates the physical force needed to make body structures move.

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MUSCLE TISSUE

• Abundant, dense tissue– 40-50% of body weight

• High metabolic activity– high energy use/output;– O2 consumption;

– CO2 production

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Functions of Muscle Tissue• Produce movement by contracting

– Locomotion & manipulation– Movement of blood, food, urine, etc through hollow

organs• Maintenance of posture• Stabilize joints

– so that other muscles can produce movement or maintain posture

• Heat production– Maintenance of body temperature.

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Three Kinds of Muscle Tissue

• Skeletal muscle: – Striated, usu. voluntary, attached to skeleton

• Cardiac muscle: – Striated, involuntary, walls of heart

• Smooth muscle: – Non-striated, involuntary, wrapping of hollow organs– Stomach, intestines, arteries, bladder, vas deferens,

uterus, etc.

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Muscle Tissue Types

· Skeletal muscle· Can be controlled

voluntarily· Cells attach to

connective tissue· Cells are striated· Cells have more than

one nucleus

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Muscle Tissue Types

· Cardiac muscle· Found only in the

heart· Function is to pump

blood (involuntary)· Cells attached to

other cardiac muscle cells at intercalated disks

· Cells are striated· One nucleus per cell

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Muscle Tissue Types

· Smooth muscle· Involuntary muscle· Surrounds hollow

organs· Attached to other

smooth muscle cells· No visible striations· One nucleus per cell

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Nervous Tissue

• Detects changes inside and outside the body and initiates and transmits nerve impulses that coordinate body activities to help maintain homeostasis.

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Nervous Tissue

· Neurons and nerve support cells

· Function is to send impulses to other areas of the body· Irritability

· Conductivity

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Tissue Repair

· Regeneration· Replacement of destroyed tissue by the

same kind of cells

· Fibrosis· Repair by dense fibrous connective tissue

(scar tissue)

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Regeneration of Tissues

· Tissues that regenerate easily· Epithelial tissue· Fibrous connective tissue and bone

· Tissues that regenerate poorly· Skeletal muscle

· Tissues that are replaced largely with scar tissue· Cardiac muscle· Nervous tissue within the brain and spinal cord