module 1 studyguide tissues

Tissues

Are collections of structurally similar cells with related function.

The entire body is composed of only four major types of tissues.

1. Muscle

2. Nervous

3. Epithelial

4. Connective

Nervous tissue

Reacts to stimuli and to conduct impulses to various organs in the body which bring about a response to the stimulus.

This tissue (as in the brain, spinal cord and peripheral nerves that branch throughout the body) are all made up of specialized nerve cells called neurons.

Neurons are easily stimulated and transmit impulses very rapidly.

All functions of epithelial tissue

Protection

Sensation Sensory stimuli

Secretion in glands

Absorption

Excretion

Diffusion

Cleaning

Reduces Friction

Epithelial Tissue Function

Protection

Epithelial cells from the skin protect underlying tissue from mechanical injury, harmful chemicals, invading bacteria and from excessive loss of water.

Epithelial Tissue Function

Sensation Sensory stimuli

penetrate specialized epithelial cells. Specialized epithelial tissue containing sensory nerve endings is found in the skin, eyes, ears, nose and on the tongue

Epithelial Tissue Function

Secretion in glands

epithelial tissue is specialized to secrete specific chemical substances such as enzymes, hormones

Epithelial Tissue Function

Absorption

Certain epithelial cells lining the small intestine absorb nutrients from the digestion of food

Epithelial Tissue Function

Excretion

Epithelial tissues in the kidney excrete waste products from the body and reabsorb needed materials from the urine. Sweat is also excreted from the body by epithelial cells in the sweat glands.

Epithelial Tissue Function

Diffusion

Simple epithelium promotes the diffusion of gases, liquids and nutrients. Because they form such a thin lining, they are ideal for the diffusion of gases (e.g.: walls of capillaries and lungs)

Epithelial Tissue Function

Cleaning

Ciliated epithelium assists in removing dust particles and foreign bodies which have entered the air passages.

Epithelial Tissue Function

Reduces Friction

The smooth, tightly-interlocking, epithelial cells that line the entire circulatory system reduce friction between the blood and the walls of the blood vessels.

Epithelial cells based on shape

Squamous

flat

Epithelial cells based on shape

Cuboidal

cube-like

Epithelial cells based on shape

Columnar

tall and rod-like

Epithelial cells based on their cell layer number

Simple

only one layer

Epithelial cells based on their cell layer number

Stratified

multiple layers

Simple squamous epithelia

Function: Reduces friction in body cavities and capillaries, and facilitates gas exchange.

Location: Are seen lining body cavities and capillaries, (reduce friction) as well as lining the alveoli (facilitate gas exchange).

Simple cuboidal epithelium

Function: secretion and absorption

Location: Found in glands and in the lining of the kidney tubules as well as in the ducts of the glands. They also constitute the germinal epithelium which produces the egg cells in the female ovary and the sperm cells in the male testes.

Simple columnar epithelium

Function: They secrete mucus or slime, a lubricating substance which keeps the surface smooth.

Location: Forms the lining of the stomach and intestines. Some columnar cells are specialized for sensory reception such as in the nose, ears and the taste buds of the tongue. Goblet cells (unicellular glands) are found in between the columnar epithelial cells of the duodenum.

Pseudostratified columnar epithelium

Function: secretion, mucus

Location: Ducts of large glands, ciliated variety lines the trachea, most upper respiratory tract

Stratified cuboidal epithelia

Function: protection

Location: ducts of sweat glands and the male urethra

Stratified columnar epithelium

Function: protection, secretion

Location: small amount in male urethra and in large ducts of some glands

Stratified squamous epithelium

Location: vagina

Transitional epithelium

Function: Stretches readily and permits distension of urinary organ by contained urine.

Location: lines the ureters, bladder, and part of the urethra

Exocrine glands

have ducts

Modes of exocrine glands

Merocrine

Form membrane-bound secretory vesicles internal to the cell. Moved to the apical surface where the vesicles coalesce with the membrane on the apical surface to release the product. MOST glands release their product in a way.

Modes of exocrine glands

Apocrine

Apical portions of cells are pinched off and lost during the secretory process. Results in a secretory product that contains a variety of molecular components including those of the membrane. Mammary glands release their products in this manner.

Modes of exocrine glands

Holocrine

Involves death of the cell. Secretory cells are released and as it breaks the contents become the secretory product.

Endocrine gland

are ductless, which enters the circulation and reaches the target tissue to have their effects

ex: Pancreas has endocrine and exocrine parts, secretes 3 hormones (insulin, glucagon, and somatostatin); endocrine part produces hormones, exocrine part produces enzymes for food breakdown and digestion

Tight junctions (zona occludens)

A type formed of junctional complex. They are formed by by claudin and occludin proteins, joining the cytoskeletons of the adjacent cells.

Function:

• they hold cells together

• they block the movement of integral membrane proteins between the apical and basolateral surfaces of the cell

• this aims to preserve the transcellular transport

• they prevent the passage of molecules and ions through the space between cells

Desmosomes

1. two disc-like plaques connected across intercellular space

2. plaques of adjoining cells are joined by proteins called cadherins

3. proteins interdigitate into extracellular space

4. intermediate filaments insert into plaques from cytoplasmic side

Gap junctions

1. passageway between two adjacent cells

2. they let small molecules move directly between neighboring cells

3. cells are connected by hollow cylinders of protein

Marfan syndrome

Is an autosomal dominant genetic disorder of the connective tissue characterized by disproportionately long limbs, long thin fingers, a relatively tall stature, and a predisposition to cardiovascular abnormalities, specifically those affecting the heart valves and aorta.

Linked to a defect in the gene on chromosome 15, which encodes a glycoprotein called fibrillin-1.

Fibrillin-1: formation of the elastic fibers found in connective tissue.

Ehlers-Danlos syndrome

is a group of rare genetic disorders affecting humans and domestic animals caused by a defect in collagen synthesis (Collagen I and III)

no treatment