The Cell and Tissues of the Human Body

Microscopic Anatomy

study of structures that are too small to be seen with the unaided eye.

Gross Anatomy

study of structures that can be see with the unaided eye.

Histology

study of tissues

A tissue is

collection of cells that perform the same or similar tasks. These cells tend to have very similar structure but are not the same.

Four primary human tissues

Epithelial (covering), connective (support), muscle (movement), and nervous (control)

Epithelial tissues are characterized by

cellularity, polarity, attachment, avascularity, innervation, and regeneration

Cellularity

epithelial tissue is made almost entirely of cells.

Polarity

epithelial cells have an apical surface and a basal surface.

Attachment

basal surface attaches to basement membrane.

Avascularity

lack blood vessels, must be near a blood supply.

Innervation

epithelial tissue is highly innervated, nerve fibers provide sensation.

Regeneration

because exposed apical surface is frequently damaged, epithelial cells are quickly replaced.

Specialized features of Epithelial tissues

Basement membrane, microvilli, and cilia

Basement membrane

found between epithelium and underlying connective tissue, provides physical support and anchoring at epithelial tissue.

Microvilli

finger like projections found at the apical surface of the cell that act to increase surface area.

Cilia

motile extensions found at the apical surface that act to move substances across the surface of the cell.

Connections between epithelial cells are

intercellular junctions

Types of junctions

1. Tight junctions

2. Adhering junctions

3. Desmosomes

4. Gap junctions

Epithelial tissues can be classfied by the _________ or ________

1. Number of layers

2. Shape of cells

Number of layers

Simple, stratified, and pseudo-stratified

Simple

one layer of cells

Stratified

more than one layer of cells

Pseudostratified

appears stratified but is actually simple. Not all of the cells reach the apical surface.

Shape of the cells at the apical surface

1. Squamous cells

2. Cuboidal cells

3. Columnar cells

4. Transitional cells

Squamous cells

cells that are flat and wise with a disc shaped nucleus

Cuboidal cells

cells that are as tall as they are wise with a spherical nucleus

Columnar cells

cells are taller than they are wide. Oval nucleus oriented length wide in the basal region of the cell.

Transitional cells

are able to change shape depending on conditions.

Endocrine glands

internal secretion; empty into the blood. Ex: hormones

Exocrine glands

external secretion; empty into ducts. Ex: sweat, oil

Connective tissues are composed of______ and _______

1. cells

2. extracellular matrix

What are the 6 main functions of epithelial tissues

1. protection - bone

2. support and framework - bone

3. bind together tissues - ligaments

4. storage - adipose

5. transport fluids and dissolved materials - blood, lymph

6. defense from microorganisms - blood, lymph

What are the 3 broad categories of connective tissue?

1. connective tissue proper

2. supporting connective tissue

3. fluid connective tissue

What are the 3 types of protein fibers in connective tissue proper?

1. collagen fibers

2. elastic fibers

3. reticular fibers

What are the two categories of connective tissue proper?

1. loose connective tissue

2. dense connective tissue

Loose connective tissue

serves as the body’s packing material, found in spaces around organs.

Dense connective tissue

strong, has fibers (mostly collagens) packed tightly together.

Loose connective tissues

1. Areolar

2. Adipose

3. Reticular

Areolar tissue

surrounding nerves, vessels, subcutaneous layer. Function: surrounds and protects, connects epithelia to deeper tissue.

Adipose tissue

subcutaneous layer; surrounding kidneys and selected other organ. Function: stores energy, cushions organs, and insulates.

Regular tissue

tendons (muscle to bone) and ligaments (bone to bone). Function: provide strength and flexibility in a single direction.

Dense connectie tissues

1. regular

2. irregular

3. elastic

Reticular tissue

spleen, liver, lymph nodes, bone marrow. Function: provides supportive framework.

Irregular tissue

dermis and capsule of organs. Function: provides tensile strength and resists stress in all directions.

Elastic tissue

found between vertebrae, vocal cords, and walls of large arteries. Function: provides framework and supports organs.

What are the two types of supporting connective tissue?

1. cartilage

2. bone

What are the 3 types of cartilage?

1. Hyaline cartilage

2. Fibrocartilage

3. Elastic cartilage

What are the two forms of bone?

1. Compact bone

2. Cancellous bone

What is the function of the bone?

protects organs

Fluid connective tissue consists of ______ and ______

1. blood

2. lymph

Function of the fluid connective tissue

transports respiratory gases, nutrients, wastes, hormones, and governs immune response.

Location of the fluid connective tissue

found in the heart and in blood vessels

Blood is made of

1. plasma

2. erythrocytes

3. leukocytes

4. platelets

plasma

watery ground substances containing proteins

erythrocytes

red blood cells

leukocytes

white blood cells

platelets

fragments of blood cells involved in blood clotting (acellular)

Lymph is derived from______

plasma

Muscle Tissue

comprised of cells called fibers. When cells are active, internal changes cause them to shorten, and the result of this shortening is movement.

What are teh 3 types of muscle tissues?

1. skeletal

2. cardiac

3. smooth

Skeletal muscle

voluntary, multinucleate, striated, and longer, cylindrical cells.

Cardiac muscle

involuntary, one nucleus, branches, striate fibers, intercalated discs.

Smooth muscle

involuntary, one nucleus, non-striated, short, thin, spindle shaped fibers.

Nervous tissue

conducts electrical impulses, detect stimuli. and process information quickly.

Neurons

comprise 20% of all nervous tissues - excitability and conductivity

Glial cells

comprise 80% of nervous tissue - supports, protects, and insulate