Cells and Tissues

Anatomy of the Generalized Cell

All cells share general structures

Carry out all chemical activities needed to sustain life.

Cells are the building blocks of all living things

Cells are not all the same

Structure reflects function

Cell Diversity

Cell Diversity

Cell Diversity

Cellular Physiology:

Membrane Transport

Membrane Transport – movement of substance into and out of the cell

Transport allows the cells to maintain homeostasis

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The plasma membrane allows some materials to pass while excluding others

This permeability includes movement into and out of the cell

Transport is by two basic methods

Passive transport

No energy is required

Active transport

The cell must provide metabolic energy

Passive Transport Processes

Diffusion

Particles tend to distribute themselves evenly within a solution

Movement is from high concentration to low concentration, or down a concentration gradient

Figure 3.8

Passive Transport Processes

Types of diffusion

Osmosis – simple diffusion of water

Highly polar water easily crosses the plasma membrane

Facilitated diffusion (glucose)

Substances require a protein carrier for passive transport

Diffusion through the Plasma

Membrane

Passive Transport Processes

Filtration

Water and solutes are forced through a membrane by fluid, or hydrostatic pressure

A pressure gradient must exist

Solute-containing fluid is pushed from a high pressure area to a lower pressure area

Active Transport Processes (ATP)

Transport substances that are unable to pass by diffusion

They may be too large

They may not be able to dissolve in the fat core of the membrane

They may have to move against a concentration gradient

Two common forms of active transport

Solute pumping

Bulk transport

Active Transport Processes

Solute pumping

Amino acids, some sugars and ions are transported by solute pumps

ATP energizes protein carriers, and in most cases, moves substances against concentration gradients

Active Transport Processes

Active Transport Processes

Bulk transport

Exocytosis

Moves materials out of the cell

Material is carried in a membranous vesicle

Vesicle migrates to plasma membrane

Vesicle combines with plasma membrane

Material is emptied to the outside

Active Transport Processes

Active Transport Processes

Bulk transport

Endocytosis

Extracellular substances are engulfed by being enclosed in a membranous vescicle

Types of endocytosis

Phagocytosis – cell eating

Pinocytosis – cell drinking

Active Transport Processes

Cellular Disease

• Abnormal cells can disrupt the internal environment of the body

• Cell Transport disorders

▫ Cystic fibrosis(CF)- condition in which Chlorine is altered and it causes abnormal secretion of sweat, mucus and pancreatic juice.

▫ Duchenne Muscular Dystrophy (DMD)- Membranes leaks excess Calcium. This triggers chemical reactions that destroy muscles.

Cellular Disease

• Cell membrane disorders ▫ Diabetes mellitus (type 2)- number of insulin

membrane receptors is reduced as a result of obesity

• Cell Reproduction ▫ Cancer- abnormal cell growth that forms tumors

which can potentially impair health

• DNA and Protein synthesis ▫ Sickle cell anemia- abnormal hemoglobin ▫ Metabolism problems

Tissues When cells come together

Body Tissues

Tissues- Groups of similar cells that perform a common function

Matrix- non-living intercellular material

Four primary types

Epithelium

Connective tissue

Muscle tissue

Nervous tissue

Epithelial Tissues Locations

Membranous

Body coverings

Body linings

Glandular tissue

Functions

Protection

Absorption

Filtration

Secretion

Sensory

Characteristics

Cells close together

Cells have free apical surface

Limited matrix

Bottom surface is basement membrane

Avascular – no blood supply

Regenerate easily

Classification of Epithelium

1. Based on # of cell layers

Simple – one layer

Stratified – more than one layer

2. Shape of cells

Squamous – flattened

Cuboidal – cube-shaped

Columnar – column-like

Type of Simple Epithelium

1. Simple squamous

Single layer of flat cells

Usually forms membranes

Lines body cavities

Lines lungs and capillaries

2. Simple cuboidal

Single layer of cube-like cells

Common in glands and their ducts

Forms walls of kidney tubules

Covers the ovaries

3. Simple columnar

Single layer of tall cells

Often includes goblet cells, which produce mucus

Lines digestive tract

4. Pseudostratified

Single layer, but some cells are shorter than others

Often looks like a double cell layer

Sometimes ciliated, such as in the respiratory tract

May function in absorption or secretion

Types of Stratified Epithelium

1. Stratified squamous

Cells at the free edge are flattened

Found as a protective covering where friction is common

Locations

Skin

Mouth

Esophagus

2. Stratified cuboidal

Two layers of cuboidal cells

3. Stratified columnar

Surface cells are columnar, cells underneath vary in size and shape

Both are:

Found mainly in ducts of large glands

Rare in human body

Glands (side note)

Gland – one or more cells that secretes a particular product

2 types

1. Endocrine gland

Ductless

Secretes hormones

2. Exocrine gland

Empty through ducts to surface

Include sweat and oil glands

4. Transitional epithelium

Shape of cells depends upon the amount of stretching

Lines organs of the urinary system

(Back to Types of Stratified Epithelium)

Connective Tissue

Location

Found everywhere in the body

Functions

Connects

Supports

Transports

Protects

Characteristics

Variations in blood supply

Some tissue types are well vascularized

Some have poor blood supply or are avascular

Extracellular matrix

Non-living material that surrounds living cells

Connective Tissue Types 1. Bone (osseous tissue)

Bone cells in lacunae (cavities)

Hard matrix of calcium salts

A lot of collagen fibers

Protect & supports body

Connective Tissue Types 2. Hyaline cartilage

Most common cartilage

Lots of collagen fibers

Rubbery matrix

Fetal skeleton & ribs

Connective Tissue Types 3. Elastic cartilage

Provides elasticity

found in external ear,

epiglottis, & trachea

Connective Tissue Types 4. Fibrocartilage

Highly compressible

forms cushion-like discs between vertebrae

Connective Tissue Types 5. Dense

Main matrix element is collagen fibers

Cells are fibroblasts

Tendon –

muscle to bone

Ligaments –

bone to bone

Connective Tissue Types

6. Areolar

Most widely distributed

Soft, pliable tissue

Contains all fiber types

Can soak up excess fluid

Think “airy”

Connective Tissue Types

7. Adipose

Similar to areolar with fat globules

Many cells contain large lipid deposits

Functions

- Insulates body

- Protects organs

- Fuel storage

Connective Tissue Types

8. Reticular

Delicate network of interwoven fibers

Forms stroma (internal supporting network) of lymphoid organs

- Lymph nodes

- Spleen

- Bone marrow

Connective Tissue Types

9. Blood

Blood cells surrounded by fluid matrix

Fibers are visible during clotting

Functions as the transport vehicle for materials

Muscle Tissue

Function = produce movement

3 types

- Skeletal muscle

move muscles of skeleton

- Cardiac muscle

only found in heart

- Smooth muscle

found in organs & vessels

Muscle

Type

Type of

Control?

Striations? How many

nuclei?

Skeletal Voluntary Yes Many per

cell

Cardiac Involuntary Yes &

intercalated

disks

1 per cell

Smooth Involuntary No 1 per cell

Nervous Tissue

Neurons and nerve support cells

Function = send impulses to other areas of the body

- Irritability – able to respond to stimuli

- Conductivity – conducts messages

Tissue Repair

Regeneration

Replacement of destroyed tissue by the same kind of cells

Fibrosis

Repair by dense fibrous connective tissue (scar tissue)

Determination of method

Type of tissue damaged

Severity of the injury

Events in Tissue Repair

Capillaries become very permeable

Introduce clotting proteins

Wall off injured area

Formation of granulation tissue

Regeneration of surface epithelium

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

Tissue Type Epithelial Connective Muscle Nerve

Cell Shape Flattened,

cuboidal,

columnar

Irregular or round Elongated Cell appendages

branched

Cell

Arrangement

Single

multilayered

Scattered in

matrix

In sheets or

bundles

Isolated or

networked

Location Body covering or

lining organs or

cavities

Supports other

organs

Lining internal

organs, make

skeletal muscles

Concentrated in

brain and spinal

cord + all over the

body

Surface Feature

of Cells

Cilia, microvilli - - -

Matrix Type Basement

membrane

Varied – protein

fibers + liquid,

gelatinous, firm to

calcified

- -

Matrix Amount Minimal Extensive Absent Absent

Unique Feature No direct blood

supply, except for

glands

Cartilage has no

blood supply

Can generate

electrical signals,

force and

movement

Can generate

electrical signal