Download The Tissue Level of Organization

The Tissue Level of Organization
Chapter 4
Four Basic Tissue Types
Epithelial
2. Connective
3. Muscle
4. neural
1.
Epithelial Tissue
 Includes epithelia and glands
 Epithelia – layers of cells that cover internal or external
surfaces
 Glands – secreting cells derived from epithelia
 Important characteristics:
 Cells bound closely together
 A free (apical) surface exposed to the environment or to some
internal chamber or passageway
 Attachment to underlying connective tissue
 By a basement membrane
 Epithelial cells that are damaged or lost at the exposed surface
are continuously replaced
Functions of Epithelia
Provide physical protection
1.
Protect exposed and internal surfaces

Control permeability
3. Provide sensation
2.
detect changes in the environment and relay the information to the
nervous system

Produce specialized secretions
4.
Gland cells
Glandular epithelium




Exocrine – secretions discharged onto the surface of the epithelium
Endocrine – secretions into the surrounding tissues and blood (hormones)
Intercellular Connections
 Must remain firmly attached to a basement membrane and
each other
 Tight junction
 Lipid layers of adjacent cell membranes are tightly bound
together by interlocking membrane proteins
 Gap junction
 Two cells are held together by embedded membrane proteins.
 Form a narrow passageway to let small molecules and ions to
pass through
 Desmosome
 Cell membranes of two cells are locked together by
intercellular cement and by membrane proteins connected to a
network of intermediate filaments
The Epithelial Surface
 Have specialized structures that distinguish them from other
body cells
 Many that line internal passageways have microvilli on their
exposed surface
 Increases surface area about 20 times
 A cell with a ciliated surface has about 250 cilia that beat in a
coordinated fashion to move materials across the surface of
the cell
 Example: the respiratory tract
The Basement Membrane
 A network of protein fibers
 Lies between the epithelium and underlying connective
tissues
 Is a place of attachment for epithelial cells
 Provides strength and resists distortion
 Is a barrier between underlying connective tissues and the
epithelium
Epithelial Renewal and Repair
 Epithelium must continually repair and renew itself
 Are lost or destroyed by chemical or physical wear and tear
 Stem cells
 Unspecialized cells
 Found deep in the epithelium near the basement membrane
 Continuously divide to replace dead or damaged cells in the
epithelium
Classifying Epithelia
 Two types of layering:
Simple
2. Stratified
1.

Three Cell Shapes:
Squamous
2. Cuboidal
3. Columnar
1.
Table 4 – 1 page 93
Cell Layers
 Simple epithelium
 Single layer of cells covering the basement membrane
 Line ventral body cavities, heart chambers and blood vessels
 Where secretions or absorption occurs – thinness reduces
diffusion time
 Stratified epithelium
 Has several layers of cells over the basement membrane
 Provides more protection
 Found in areas subject to more mechanical or chemical stress
Cell Shape
Squamous epithelium
1.


Cells are thin and flat
Looks like fried eggs laid side by side
Cuboidal epithelium
2.

Hexagonal boxes in 3D view, but in sectional view look like
boxes
Columnar epithelium
3.


Also hexagonal but taller and more slender
Nuclei are crowded in a narrow band close to basement
membrane
Simple Squamous Epithelia
 Found in protected regions where absorption takes place or
where a slippery surface reduces friction
Simple Cuboidal Epithelium
 Provides limited protection
 Secrete enzymes and buffers in the pancreas and salivary glands
 Involved in the production of urine
Simple Columnar
 Provides some protection and allow for absorption and
secretion
 Lines the stomach, intestinal tract and many excretory ducts
Pseudostratified Epithelia
 Nuclei are at varying distances from surface, it has a layered
appearance
 Pseudostratified columnar epithelium
 It is not stratified, all cells touch basement membrane
 Typically possess cilia
 Lines most of the respiratory tract
Transitional and Stratified
 Transitional epithelium
 Withstands considerable stretching
 Lines ureters and urinary bladder
 Stratified squamous epithelium
 Found where mechanical stresses are severe
 Surface of the skin, lining of mouth, tongue and esophogus
Figure 4 – 4 and 4 – 5, pgs. 95&96
Glandular Epithelia
 Produce exocrine or endocrine secretions
 Exocrine
 Discharge products through a duct onto some internal or
external surface
 Can be characterized as unicellular glands (goblet cells) or
multicellular glands (secretory sheet)
 Endocrine (hormones)
 Produced by ductless glands and released into blood or tissues
Mode of Secretion
 Each glandular cell releases secretions by one of three
mechanisms:
1. Merocrine secretion



Apocrine secretion
2.


3.
Most common mode of secretion
Product released in vesicles by exocytosis
Mucus
Involves loss of both cytoplasm and secretory product
Outermost portion of cytoplasm becomes packed with
secretory vesicles and is the shed
Holocrine secretion
 Entire sell becomes packed with secretions and then bursts
apart and dies
 Sebaceous glands
Modes of Secretion
Type of Secretion
 Exocrine glands can be categorized as serous, mucous or
mixed
 Serous Glands
 Watery solution containing enzymes
 Mucous glands
 Secrete mucins that form a thick, slippery mucus
 Mixed glands
 Contain both serous and mucous glands together
Connective Tissues
 All have three basic components:
Specialized cells
2. Protein fibers
3. Fluid known as ground substance
1.
Protein fibers and ground substance form the matrix that
surrounds the cells


Accounts for most of the volume of connective tissue
Connective Tissue Functions
 Support and Protection
 Bony structural framework
 Protect delicate organs
 Transportation of materials
 Fluid connective tissues
 Storage of energy reserves
 Adipose cells (fat)
 Defense of the body
 Antibodies
Classifying Connective Tissues
Connective tissue proper
1.


Many types of cells and matrix fibers in a ground substance
Tissue under skin, fatty tissue, and tendons and ligaments
Fluid connective tissues
2.


Distinct cells in a watery ground substance with dissolved
proteins
Blood and lymph
Supporting connective tissues
3.


Matrix of dense ground substance and closely packed fibers
Cartilage and bone
Connective Tissue Proper
 Some cells are “permanent residents,” and others are not
always present because they leave to defend and repair areas
of injured tissue
The Cell Population
 Fibroblasts – most abundant cells
 Produce and maintain connective tissue fibers and ground
substance
 Macrophages – “big eater” cells
 Phagocytize damaged cells or pathogens
 Mobilize immune system
 Fat cells – adipocytes
 Large droplet of lipid that pushes nucleus and organelles to one
side of the cell
 Mast cells – found near blood vessels
 release chemicals to begin body’s defensive activities after an
injury or infection
 Antibodies, white blood cells and stem cells
Connective Tissue Fibers
Collagen fibers
1.


Long, straight and unbranched
Strong and flexible, most common
Elastic fibers – contain protein elastin
2.

After stretching return to original length
Reticular fibers – least common
3.

Commonly form a branching, interwoven framework in
various organs
Ground Substance
 Fills spaces between cells and surrounds fibers
 Clear, colorless and has consistency of maple syrup
 Slows movement of bacteria and other pathogens
Loose Connective Tissue
 Areolar tissue
 Contains all cells and fibers found in connective tissue proper
 Extensive blood supply
 Forms a layer that separates the skin from underlying muscles
 Provides padding and allowing movement
Adipose Tissue; Figure 4 – 9 pg. 102
 Loose connective tissue containing large numbers of fat cells
 Provides more padding and shock absorption for body
 Insulation and energy storage
Dense connective tissue
 Mostly collagen fibers
 Two types: dense regular and dense irregular
 Dense regular connective tissue
 Collagen fibers packed tightly, parallel to one another
 Tendons – attach muscle to bone
 Ligaments – attach bone to bone; often contain elastic fibers
 Dense irregular connective tissue
 Interwoven network of collagen fibers
 Provides support to areas subjected to stresses from many
directions
Fluid Connective Tissues
 Blood and lymph
 Proteins dissolved in watery matrix do not form fibers
 Watery matrix is plasma in blood
 Red blood cell – makes up ½ of volume of blood
 Transport oxygen
 White blood cell – component of immune system
 Platelets – cell fragments that function in blood clotting
 Lymph forms as interstitial fluid enters small passageways, or
lymphatic vessels
 Cells of immune system monitor the composition of lymph
Supporting Connective Tissues
 Cartilage and bone
Cartilage
 Matrix of a firm gel with embedded fibers
 Chondrocytes – only cells found in matrix
 Live in small pockets called lacunae
 Avascular – limits repair capabilities
 Perichondrium
 Structure that separates cartilage from surrounding tissues
TYPES OF CARTILAGE
Hyaline cartilage – most common
1.



Closely packed collagen fibers
Tough but flexible
Connects ribs to sternum, supports respiratory tract, and
covers opposing bone surfaces
Elastic cartilage – numerous elastic fibers
2.

Elastic flap of ear and epiglottis
Fibrocartilage – little ground substance, lots of collagen
3.



Extremely durable and tough
Spinal column, between pubic bones and pelvis and in a few
joints
Resist compression, absorb shocks and prevent damaging
bone – bone contact
Figure 4 – 10, page 104
Bone (osseous tissue)
 Lacunae contain osteocytes (bone cells) and surround
blood vessels
 Canaliculi
 Branching network within bony matrix
 Periosteum
 Covering of bone that has outer fibrous and inner cellular layers
 Table 4 – 3 page 105
Membranes
 Form barriers or cover and protect structures and tissues
 Four types:
Mucous membranes
2. Serous membranes
3. Cutaneous membranes
4. Synovial membranes
1.
Mucous Membranes
 aka mucosae, line cavities that communicate with exterior
 Kept moist at all times
 Most lined by simple epithelia
 Also simple columnar, stratified squamous and transitional
squamous
 Line the digestive, respiratory, reproductive and urinary
tracts
Serous Membranes
 Line the sealed, internal subdivisions of the ventral body
cavity
 Three kinds:
Pleura – covering the lungs
2. Peritoneum – lines organs of abdominal cavities
3. Pericardium – covers the heart
1.
 Has parietal and visceral portions
 Friction is reduced by water, serous fluid
The Cutaneous Membrane
 Skin
 Covers surface of the body
 Thick, relatively waterproof, and usually dry
Synovial Membranes
 Joins or articulations are surrounded by a synovial
membrane
 Ends of bones are covered by hyaline cartilage and separated
by viscous synovial fluid
 Helps lubricate the joint and permits smooth movement
Muscle Tissue
 Specialized for contraction
 Involves interaction between filaments of myosin and actin
 Three types in the body:
Cardiac
2. Skeletal
3. Smooth
1.
Skeletal Muscle Tissue
 Contains large, multinucleated cells
 Are usually called muscle fibers
 Produced through division of stem cells
 Partial repairs can occur after injury
 Marked by a series of bands called striations
 Nervous system provides voluntary control over its activities
 Striated voluntary muscle
Cardiac Muscle Tissue
 Only found in the heart
 Cells are interconnected at intercalated discs
 Specialized attachment sites containing gap junctions and
desmosomes
 Very limited ability to repair itself
 Do NOT rely on nerve activity
 Specialized cells called pacemaker cells establish a regular rate of
contraction
 striated involuntary muscle
Smooth Muscle Tissue
 Walls of blood vessels, around hollow organs, and in layers
around the respiratory, circulatory, digestive and
reproductive tracts
 No striations
 Cells are able to divide
 Regenerate after injury
 Nonstriated involuntary muscle
Neural Tissue
 Specialized for conduction of electrical impulses from one
region of the body to another
 Two types of cells:
 Neurons – communicate through electrical events that
affect their cell membranes
 Neuroglia - provide physical support for neural tissue,
maintain the chemical composition of the tissue fluids, supply
nutrients to neurons and defend the tissue from infection
Neurons
 Longest cells in your body (up to 39 in.)
 Cannot divide – very limited ability to repair themselves
 Contain three parts:
Cell body – w/ large nucleus
2. Dendrites – numerous branching projections
3. Axon – long and slender part, communicate with other cells
1.
 End at synaptic terminals
Tissue Injuries and Repair
 Inflammation – area is isolated from healthy tissue while
damaged cells are cleaned up.
 Swelling, warmth, redness and pain
 Regeneration – second phase of following injury
 Fibroblasts produce dense network of collagen fibers known as
scar tissue or fibrous tissue
 Over time, scar tissue is remodeled and resumes normal
appearance
 Is more successful in some tissues than others
 Permanent replacement of normal tissues is called fibrosis