Anatomy & Physiology
Chapter 4 Notes: Tissues
I. Tissues: collections of cells and cell products that perform
specific, limited functions.
A) Histology: The study of t issues
Four types of tissues
1. Epithelial
2. Connective
3. Muscle
4. Neural
1. Epithelial Tissue
● Covers body surfaces
● Lines cavities
● Lines tubular structures
● Serves essential functions
a) Characteristics of Epithelial Tissue
- Cellularity (cell j unctions: Things that hold cells together)
- Polarity (a pical and basal surfaces)
- Attachment
- Avascularity: Without blood supply/vessels
- Regeneration
b) Functions of Epithelia
- Provide physical protection
- Control p ermeability: Ability to allow fluid/moisture through
- Provide sensation
- Produce specialized secretions (glandular epithelium)
Exocrine glands
Endocrine glands
c) The Epithelial Surface
Apical s urface is exposed
● Basal surface is connected to deeper connective tissue with the
basement membrane
d) Epithelial Renewal and Repair
● Epithelia are replaced by mitosis.
● Cell division of stem c ells (g erminative cells)
● Occurs near b asement membrane
e) Classification of Epithelia
● Combines a cell shape with the number of layers of cells
Example: Simple (one layer) cuboidal (square shape)
II. Cell Layers and Cell Shapes
Classification based on layers
• Simple epithelium: single layer of cells
• Stratified epithelium: several layers of cells
Classification based on shape
• Squamous epithelia: thin and flat
• Cuboidal epithelia: square shaped
• Columnar epithelia: tall, slender rectangles
a) Glandular Epithelia
Endocrine glands
● Release hormones into interstitial fluid and plasma
● No ducts
Exocrine glands
● Produce secretions:
● Onto epithelial surfaces
● Through ducts
b) Glandular Secretion
● Merocrine secretion
Released by vesicles (e xocytosis)
Example: sweat glands
● Apocrine secretion
Released by shedding cytoplasm
Example: mammary glands
● Holocrine secretion
Released by cells bursting, killing gland cells
Example: sebaceous glands
Types of Secretion
Serous glands
watery secretions
Mucous glands
Secrete mucins
Mixed exocrine glands
Both serous and mucous
III. Connective Tissue
Function: Provides a protective structural framework for other tissue types
Three basic components
1. Specialized cells
2. Solid extracellular protein f ibers
3. Fluid extracellular ground substance
Characteristics of Connective Tissue
● The extracellular components of connective tissues (fibers and ground
substance) make up the matrix.
● Majority of tissue volume
● Determines specialized function
Functions of Connective Tissue
● Support and protection.
● Transportation of materials
● Storage of energy reserves
● Defense of the body
Three Major Types of C onnective Tissue
1. Connective tissue proper
2. Fluid connective tissues
3. Supporting connective tissues
a) Cells of Connective Tissue Proper
● Fibroblasts: Produces collagen and other fibers
• Most abundant cells in connective tissue proper
• Produce connective tissue fibers and ground substance
● Macrophages: White blood cells that eat debris and
“bad guys”
- Scattered throughout the matrix
- Phagocytize d amaged cells or pathogens that enter the
tissue
- Release chemicals that mobilize the immune system
● Fat cells (a dipocytes)
- Permanent residents
- Number of fat cells vary
● Mast cells
- Small, mobile cells often found near blood vessels
- Filled with chemicals that are released to begin body's
defensive activities after an injury or infection
Three Basic Types of Connective Tissue F IBERS
1. Collagen fibers
● Long, straight, unbranched
● Strong, but flexible
● Most common
2. Elastic fibers
● Branched and wavy
● After stretching, they will return to their original
length
● Contain the protein elastin
3 . Reticular fibers
● Made of same protein subunits as collagen fibers, but
arranged differently
● Thinner than collagen fibers
● Form branching, interwoven framework in various
organs
● Least common
Ground Substance
● Clear, colorless, and v iscous
● Fills spaces between cells and slows bacterial and pathogen
movement
A. Types of Connective Tissue
Proper
● Loose connective tissue
- "Packing materials" of the
body
- More ground substance, fewer
fibers
E xample: fat (adipose tissue)
● Dense connective
tissue
- Tough, strong, and
durable
- More fibers, less
ground substance
E xample:
Tendons
B. Fluid Connective Tissues
● Blood and lymph
Watery matrix of dissolved proteins
● Red blood cells
● White blood cells
● Platelets
c. Supporting Connective Tissues
● Cartilage
Gel-type ground substance
For shock absorption and protection
● Bone
Calcified (made rigid by calcium salts, minerals)
For weight support
1. Cartilage
● Cartilage matrix
Ground substance proteins
● Chondrocytes (cartilage cells)
Surrounded by lacunae (chambers)
Cartilage Structure
● Avascular
- Chondrocytes found in pockets
called lacunae
● Perichondrium
- Outer, fibrous layer (for strength)
- Inner, cellular layer (for growth and
maintenance)
Three Major Types of Cartilage
a. Hyaline cartilage
- Stiff, flexible support
- Reduces friction between bones
- Found in synovial joints, rib tips, sternum, and trachea
b. E lastic cartilage
- Supportive but bends easily
- Found in external ear and epiglottis (area in the throat)
c. Fibrocartilage
- Limits movement
- Prevents bone-to-bone contact
- Pads knee joints
- Found between pubic bones and intervertebral discs
2. Bone (o sseous tissue)
- Strong (hard calcium compounds)
- Resists shattering (flexible collagen fibers)
● Bone cells or o steocytes
- Arranged around central canals within matrix
- Small channels through matrix (c analiculi) access blood supply
3. Tissue Membranes
Membranes are:
• Are physical barriers
• Line or cover portions of the body
• Consist of an epithelium
• Supported by connective tissues
Four Types of Tissue Membranes
1. Mucous membranes 2. Serous membranes
3. Cutaneous membrane 4. Synovial membranes
1. Mucous Membranes (aka mucosae)
- Lines passageways that have external connections
- In digestive, respiratory, urinary, and reproductive tracts
- Epithelial surfaces must be moist
- To reduce friction
- To facilitate absorption and excretion
- Made of areolar tissue (this portion is called l amina propria)
2. Serous Membranes
- Line cavities not open to the outside
- Are thin but strong
- Have fluid transudate to reduce friction
- Have a parietal portion covering the cavity
- Have a visceral portion (serosa) covering the organs
Three Serous Membranes
a. Pleura
- Lines pleural cavities
- Covers lungs
b. Peritoneum
- Lines peritoneal cavity
- Covers abdominal organs
c. Pericardium
- Lines pericardial cavity
- Covers heart
3. The Cutaneous Membrane (skin)
- Covers the surface of the body
- Thick, waterproof, and dry
4. Synovial Membranes
- Line moving, articulating joint cavities
- Produce synovial fluid (lubricant)
- Protect the ends of bones
- Lack a true epithelium
IV. Three Types of Muscle Tissue
1. Skeletal muscle tissue
- Large body muscles responsible for movement
2. Cardiac muscle tissue
- Found only in the heart
3. Smooth muscle tissue
- Found in walls of blood vessels
- Found around hollow organs such as the urinary bladder
- Around the respiratory, digestive, and reproductive tracts
a. Functions of Muscle Tissue
- Specialized for contraction
- Produces all body movement
V. Neural Tissue (AKA nervous or nerve tissue)
- Specialized for conducting electrical impulses
- Rapidly senses internal or external environment
- Processes information and controls responses
● Concentrated in the central nervous system
- Brain
- Spinal cord
Two Kinds of Neural Cells
1. Neurons
• Nerve cells
• Perform electrical communication
2. Neuroglia
• Supporting cells
• Repair and supply nutrients to neurons
Cell Parts of a Neuron
● Cell body
- Contains the nucleus and nucleolus
● Dendrites
- Short branches extending from the cell body
- Receive incoming signals
● Axon (nerve fiber)
- Long, thin extensions of the cell body
- Carries outgoing electrical signals to their destination
VI. Tissue Injuries and Repair
● Tissues respond to injuries to maintain homeostasis
- Cells restore homeostasis with two processes
1. Inflammation
2. Regeneration
Inflammation
● Inflammatory response
The tissue's first response to injury
Signs and symptoms include:
Swelling Redness
Heat Pain
● Can be triggered by:
-Trauma (physical injury)
- Infection (the presence of harmful pathogens)
Aging and Tissue Structure
● With age the rate of tissue repair declines and the rate of cancer
increases
● Speed and efficiency of tissue repair decrease with age due to:
- Slower rate of energy consumption (metabolism)
- Hormonal alterations
- Reduced physical activity
Aging and Cancer Incidence
- 1 in 4 people in the United States develops cancer
- Cancer is the #2 cause of death in the United States
- Environmental chemicals and cigarette smoke cause cancer