What are the four tissues of the body?

Our body is made from these 4 tissues

Epithelial Tissue

Covers exposed surfaces

Lines internal passageways

Forms glands

Connective Tissue

Fills internal spaces

Supports other tissues

Transports material - cells

Stores energy

Muscle Tissue

Specialized for contraction

Skeletal muscle, heart muscle, and walls of hollow organs

Neural Tissue

Carries electrical signals from 1 part of the body to another

KEY CONCEPT

Tissues are collections of cells and cell products that perform specific, limited functions

4 tissue types form all the structures of the human body:

epithelial, connective, muscle, and neural

What are the special structures and functions of epithelial tissues?

Characteristics of Epithelia

1. Cellularity (cell junctions)

2. Polarity (apical and basal surfaces)

3. Attachment (basal lamina)

4. Avascularity

5. Regeneration

Functions of Epithelial Tissue

1. Provide physical protection

2. Control permeability

3. Provide sensation

4. Produce specialized secretions (glandular epithelium)

Specializations of Epithelial Cells

1. Move fluids over the epithelium (protection)

2. Move fluids through the epithelium (permeability)

3. Produce secretions (protection and messengers)

Figure 4–1

Free Surface and Attached Surface

Polarity: apical and basolateral surfaces

Increasing Surface Area

Microvilli increase absorption or secretion

Cilia (ciliated epithelium) move fluids

Effective Barriers

Physical integrity is maintained by:intercellular connections

attachment to basal lamina

maintenance and repair

Cell Junctions

Form bonds with other cells or extracellular material:

tight junctions

gap junctions

desmosomes

Tight Junctions

Between 2 cell membranes

Figure 4–2b

Tight Junctions

Adhesion belt attaches to terminal web

Prevents passage of water and solutes

Isolates wastes in the lumen

Gap Junctions

Allow rapid communications

Figure 4–2c

Gap Junctions

Held together by channel proteins (junctional proteins, connexons)

Allow ions to pass

Coordinated contractions in heart muscle

Desmosomes

CAMs, dense areas, and intercellular cement

Figure 4–2d

Desmososmes

Button desmosomes

Ties cells together

Allow bending and twisting

Attachment to Basal Lamina

Hemidesmosomes

Figure 4–2e

Basal Lamina

Lamina lucida: thin layer secreted by epitheliabarrier to proteins

Lamina densa: thick fibersproduced by connective tissuestrength and filtration

Repairing and Replacing Epithelia

Epithelia are replaced by division of germinative cells (stem cells)

Near basal lamina

Classes of Epithelia

Based on shape and layers

Table 4–1

Layers

Simple epithelium: single layer of cells

Stratified epithelium:several layers of cells

Cell Shape

Squamous epithelia:flat shaped

Cuboidal epithelia:square shaped

Columnar epithelia:tall shaped

Squamous Epithelia

Simple squamous epithelium: absorption and diffusion

Mesothelium: lines body cavities

Endothelium: lines heart and blood vessels

Figure 4–3a

Simple Squamous Epithelium

Figure 4–3b

Stratified Squamous Epithelium

Stratified Squamous Epithelium

Protects against attacks

Keratin proteins add strength and water resistance

Cuboidal Epithelia

Simple cuboidal epithelium:secretion and absorption

Stratified cuboidal epithelia:sweat and mammary ducts

Simple Cuboidal Epithelium

Kidney tubules

Figure 4–4a

Stratified Cuboidal Epithelium

Sweat gland ducts

Figure 4–4b

Transitional Epithelium

Urinary bladder

Figure 4–4c

Columnar Epithelia

Simple columnar epithelium:absorption and secretion

Pseudostratified columnar epithelium:cilia movement

Stratified columnar epithelium:protection

Simple Columnar Epithelium

Intestinal lining

Figure 4–5a

Pseudostratified Columnar Epithelium

Trachea

Figure 4–5b

Stratified Columnar Epithelium

Salivary gland duct

Figure 4–5c

Mechanisms of Glandular SecretionPLAYPLAY

Glandular Epithelia

Endocrine and exocrine glands

Figure 4–6

Endocrine Glands

Release hormones:into interstitial fluid

no ducts

Exocrine Glands

Produce secretions:onto epithelial surfaces

through ducts

Modes of Secretion

Merocrine secretion (GA produces and secreted by vesicles)

Figure 4–6a

Modes of Secretion

Apocrine secretion (GA produces and released by shedding cytoplasm)

Figure 4–6b

Modes of Secretion

Holocrine secretion (released by bursting and killing the cell)

Figure 4–6c

Types of Secretions

Serous glands:watery secretions

Mucous glands:secrete mucins

Mixed exocrine glands:both serous and mucous

Gland Structure

Exocrine glands can be classified as:unicellular glands

multicellular glands

Structure of Multicellular Exocrine Glands

Structural classes of exocrine glands

Figure 4–7 (1 of 2)

Structure of Multicellular Exocrine Glands

Figure 4–7 (2 of 2)

What are the structures and functions of different types of connective tissues?

Connective Tissues

Connect epithelium to the rest of the body (basal lamina)

Provide structure (bone)

Store energy (fat)

Transport materials (blood)

Have no contact with environment

The Matrix

The extracellular components of connective tissues (fibers and ground substance):

majority of cell volume

determines specialized function

Classification of Connective Tissues

Connective tissue proper:connect and protect

Fluid connective tissues:transport

Supportive connective tissues:structural strength

Connective Tissue Proper

Figure 4–8

Categories of Connective Tissue Proper

Loose connective tissue:more ground substance, less fibers

e.g., fat (adipose tissue)

Dense connective tissue:more fibers, less ground substance

e.g., tendons

8 Cell Types of Connective Tissue Proper

Fibroblasts

Macrophages

Adipocytes

Mesenchymal cells

Melanocytes

Mast cells

Lymphocytes

Microphages

Fibroblasts

The most abundant cell type:found in all connective tissue proper

secrete proteins and hyaluronan (cellular cement)

Makes ground substance and structural fibers

Macrophages

Large, amoeba-like cells of the immune system:

eat pathogens and damaged cells

fixed macrophages stay in tissue

free macrophages migrate

Adipocytes

Fat cells: each cell stores a single, large fat droplet

Mesenchymal Cells

Stem cells that respond to injury or infection:

differentiate into fibroblasts, macrophages, etc.

Melanocytes

Synthesize and store the brown pigment melanin

Mast Cells

Stimulate inflammation after injury or infection:

release histamine and heparin

Basophils are mast cells carried by blood

Lymphocytes

Specialized immune cells in lymphatic system:e.g., plasma cells which produce antibodies

Microphages

Phagocytic blood cells:respond to signals from macrophages and mast cells

e.g., neutrophils and eosinophils

Fibers in Connective Tissue Proper

Collagen fibers: most common fibers in CTP

long, straight, and unbranched

strong and flexible

resists force in 1 direction

e.g., tendons and ligaments

Fibers in Connective Tissue Proper

Reticular fibers: network of interwoven fibers (stroma)

strong and flexible

resists force in many directions

stabilizes functional cells (parenchyma) and structures

e.g., sheaths around organs

Fibers in Connective Tissue Proper

Elastic fibers: contain elastin

branched and wavy

return to original length after stretching

e.g., elastic ligaments of vertebrae

Loose Connective Tissues

The packing materials of the body

3 types in adults:areolar

adipose

reticular

Areolar Tissue

Least specialized

Open framework

Viscous ground substance

Elastic fibers

Holds blood vessels and capillary beds:e.g., under skin (subcutaneous layer)

Adipose Tissue

Contains many adipocytes (fat cells)

Figure 4–10a

Adipose Cells

Adipocytes in adults do not divide:expand to store fat

shrink as fats are released

Mesenchymal cells divide and differentiate:

to produce more fat cells

when more storage is needed