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From Cells to Organ Systems

Epithelial Tissues

consist of sheets of cells that line or cover various surfaces and body cavities
ex: (skin, lining of the mouth, inner surface of digestive track, lungs, bladder, blood vessels, and tubules of kidnesy

Glands (glandular epithelia)

form the body's glands. epithelial tissues that are specialized to synthesize and secrete a product.

Exocrine glands

(exo- means "outside" or "outward") secrete their products into a hollow organ or duct.
ex: secrete saliva, sweat glands in your skin, and glands in your stomach that produce digestive acid.

Endocrine Glands

(endo- means "within") secrete substances called hormones into the blood stream.
ex: thyroid gland, which secretes several hormones that help your body's growth and metabolism.


groups of specialized cells that are similar in structure and that perform common functions.
4 major types of tissues
1. Epithelial
2. Connective
3. Muscle
4. Nervous

Squamous epithelium

consists of one or more layers of flattened celled. (squama means "platelike") (appears "squashed flat"
- forms outer surface of skin and lines the inner surfaces of the blood vessels, air sacs of the lungs, mouth and throat and vagina
- permits exchange of nutrients, wastes, and gases.

cuboidal epithelium

composed of cube-shaped cells
- forms the kidney tubules, glands, and covers the surface of the ovaries
- secretes and reabsorbs water and small molecules.

Columnar Epithelium

composed of tall, rectangular (column-shaped) cells.
- lines parts of the digestive tract, certain reproductive organs, and the larynx
- goblet cell within the simple columnar secrete mucus, a thick fluid that lubricates the tissues and traps bacteria, viruses, and irritating particles.
- absorbs nutrients, produces mucus.

Stratified squamous

- outer layer of skin, mouth, vagina
- protects against abrasion, drying out infection

Stratified cuboidal

- Lines ducts of sweat glands
- secretes water and ions

Stratified columnar

- lines epididymus, mammary glands, larynx
- secretes mucus

Basement membrane

directly beneath the cells of an epithelial tissue is a supporting non-cellular layer

cell junctions

1. tight junction
2. Adhesion junctions
3. Gap junctions

Tight junctions

- form leak-proof seals between cells.
- tight junctions are particularly important in epithelial layers that must control movement of substances into or out of the body.
- cells that line the digestive tract (which bring in nutrients), bladder (which stores urine), cells that form the tubules of the kidneys (which remove waste products from the body)

Adhesion junction

-sometimes called spot desmosomes
-looser in structure
- protein filaments of adhesion junctions
- allows for some movement between cells, gives the tissues the ability to stretch and bend
- found in the epithelium of your skin

Gap Junctions

represent connecting channels mad of ptoteins the permit movement of ions or water between two adjacent cells
-found in the epithelial cells in the liver, heart and some muscle tissue

Connective tissue

supports the softer organs of the body against gravity and connects the parts of the body together.

Collagen fibers

made of protein, confer strength and are slightly flexiable.

Elastic Fibers

most fibrous connective tissues also contain thinner coiled elastic fibers, made primarily of the protein elastin, which can stretch without breaking.

Fibrous Connective Tissue

1. Loose
2. Dense
3. Elastic
4.. Reticular (lymphoid)

Specialized Connective Tissues

1. Cartilage
2. Bone
3. Blood
4. Adipose tissue

Loose Fibrous Connective Tissue

- also called areolar connective tissue
- Mostly collagen and elastin fibers in no particular pattern; more ground substance
- Flexible but only moderately strong
- Surrounds internal organs, muscles, blood vessels

Dense Fibrous Connective Tissue

- Mostly collagen in a parallel arrangement of fibers; less ground substance.
- Strong
- In tendons, ligaments, and lower layers of skin.

Elastic Fibrous Connective Tissue

- High proportion of elastin fibers
- Stretches and recoils easily
- Surrounds hollow organs that change in shape or size regularly

Reticular (lymphoid) Fibrous Connective tissue

- Mostly thin, interconnecting reticular fibers of collagen
- Serves as a flexible internal framework.
- In soft organs such as liver, spleen, tonsils, and lymph glands.

Specialized Connective Tissues - Cartilage

- Primarily collagen fibers in a ground substance containing a lot of water
- Maintains shape and resists compression
- Embryonic tissue that becomes bone. Also the nose, vertebral disks, and the lining of joint cavities.

Specialized Connective Tissues - Bone

- Primarily hard mineral deposits of calcium and phosphate.
- Very Strong
- Forms the skeleton

Specialized Connective Tissues - Blood

- Blood cells, platelets, and blood fluid called plasma
- Transports materials and assists in defense mechanisms
- Within cardiovascular system

Specialized Connective Tissues - Adipose Tissue

- Primarily cells called adipocytes filled with fat deposits
- Stores energy in the form of fat
- Under the skin, around some internal organs.

Reticular Fibers

Fibrous connective tissue contains thin fiber of collagen, called reticular fibers, that interconnect with each other


are the cells responsible for producing and secreting the proteins that compose the collagen, elastic, and reticular fibers.

Muscle Tissue

Consists of cells that are specialized to shorten, or contract, resulting in movement of some kind.
Muscle tissue is composed of tightly packed cells called muscle fibers.

Skeletal muscle tissue

Connects to tendons, which attach to bones.
When skeletal muscles contract, they cause body parts to move.
The individual fibers are thin cylinders.

Cardiac muscle tissue

(Greek kardia, the heart) is found only in the heart. The individual cells are much shorter than skeletal muscle fibers, they only have one nucleus.
Arranged parallel to each other.

Smooth muscle tissue

surrounds hollow organs and tubes, including blood vessels, digestive tract, uterus, and bladder.
These slim cells are much smaller than skeletal muscle cells, and have only one nucleus, like cardiac muscle.

Nervous tissue

consists primarily of cells that are specialized for generating and transmitting electrical impulses throughout the body.


Nervous tissue cells that generate and transmit electrical impulses are called neurons.
1. the cell body - where the nucleus is located
2. dendrites - numerous cytoplasmic extensions the extend from the cell body and receive signals from other neurons
3. axon - the long extension the transmits electrical impulses over long distances

Glial cell

another type of nervous tissue that does not transmit electrical impulses.


structures composed of two or more tissue types joined together that perform a specific function or functions.

Organ systems

groups of organs that together serve a broad function that is important to survival either of the individual organism (such as respiration, movement, or excretion of waste) or of the species (reproduction).

Integumentary System

-Protects us from injury, infection, and dehydration
-Participates in temperature control
-Receives sensory input from the external environment.

Skeletal System

-Protects, supports, and anchors body parts
-Provides the structural framework for movement
-Produces blood cells
-Stores minerals

Muscular system

-produces movement or resists movement
-Generates heat

nervous system

-Detects both external and internal stimuli
-Controls and coordinates rapid responses to these stimuli
-integrates the activities of other organ systems.

Endocrine system

-Produces hormones that regulate many body functions
-participates with the nervous system in integrative functions

Digestive system

-Provides the body with water and nutrients
-(the liver) synthesizes certain proteins and lipids for the body
-(the liver) inactivates many chemicals, including hormones, drugs, and poisons.

Circulatory system

-transports materials to and from all cells
-participates in the maintenance of body temperature
-participates in mechanisms of defense against disease and injury.

Lymphatic system

-returns excess tissue fluid to the circulatory system
-participates in both general and specific (immune) defense responses

Respiratory system

-Exchanges gases (oxygen and carbon dioxide) between air and blood.
-Participates in the production of sound (vocalization)

Urinary system

- Maintain the volume and composition of body fluids
- excretes some waste products

Reproductive system

- Female: Produces eggs
-Female: Nurtures the fertilized egg, developing embryo, and fetus until birth
-Male: Produces sperm
-Male: Participates in the delivery of sperm to the female

Tissue Membranes

consisting of a layer of epithelial tissue and a layer of connective tissue line each body cavity and form our skin.
1. Serous membranes
2. Mucous membranes
3. Synovial membranes
4. Cutaneous membrane

Serous membranes

line and lubricate body cavities to reduce friction between internal organs

Mucous membranes

line the airways, digestive tract, and reproductive passages. Goblet cells within the epithelial layer secrete mucus, which lubricates the membrane's surface and entraps foreign particles.

Synovial membranes

Line the very thin cavities between bones in movable joints. These membranes secrete a watery fluid that lubricates the joint.

Cutaneous membrane

Our outer covering. known as the skin and it serves several functions.

integumentary system

(form the Latin integer, meaning "to cover"). the proper name fo rthe skin and it accessory structures such as hair, nails, and glands.


the outer layer of the skin's epithelial tissue


the inner layer of connective tissue


(hypo- means "under"), consisting of loose connective tissue containing fat cells. This is a supportive layer which supports the dermis and epidermis.


the more numerous of the two types of skin cells. the cells produce a tough, waterproof protein called keratin. sometimes called basal cells


less numerous cells, located near the base of the epidermis produce a dark-brown pigment called melanin.


the surface of the dermis has many small projections called papillae that contain sensory nerve ending and small blood vessels.

Internal environment

the environment that surrounds the cells of a multicellular organism (their external environment)

interstitial fluid

the internal environment if a clear fluid. (the Latin noun interstitium means "the space between", in this case the space between cells)


relative constancy of the conditions within the internal environment. (homeo- means "unchanging" or "the same" and -stasis means "standing")

Negative feedback

in living organisms, homeostasis is maintained by negative feedback control systems

controlled variable

a controlled variable is any physical or chemical property that might vary from time to time and that must be controlled to maintain homeostasis.


(or receptor). the sensor monitors the current value of the controlled variable and sends the information (via either nerves or hormones) to the control center.

Control Center

the control center receives input from the sensor and compares it to the correct, internally set value of the controlled variable, this is sometime called the set point. Signals are sent via either nerves or hormones.


the effector takes the necessary action to correct the imbalance, in accordance with the signals it receives from the control center


a neural struture lying below the thalamus; it directs several maintenance activities, helps govern the endocrine system via the pituitary gland, and is linked to emotion

Positive feedback

control systems are relatively uncommon in living organisms. In positive feedback, a change in the controlled variable sets in motion a series of events that amplify the original change, rather that returning it to normal.

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