1. Body Tissues Ch.3 (Part II)
The human body, complex as it is, starts out as a single cell, the fertilized egg, which divides almost endlessly. The millions of cells that result become specialized for particular functions. Some become muscle cells, otehrs the transparent lens of the eye, still others skin cells, and so on. Thus, there is a division of labor in the body, with certain groups of highly specialized cells performing functions that benefit the organism as a whole.
Cell specialization carries with it certain hazards. When a small group of cells is indispensable, its loss can disable or even destroy the body. For example, the action of the heart depends on a very specialized cell group in the heart muscle that controls its contractions. If those particular cells are damaged or stop functioning, the heart will no longer work efficiently, and the whole body will suffer or die from lack of oxygen.
Ch.3 (Part II)

2. Body Tissues Cells are specialized for particular functions Tissues
Groups of cells with similar structure and function
Four primary types
Epithelium
Connective tissue
Nervous tissue
Muscle

3. Body Tissues
If we had to assign a single term to each primary tissue type that would best describe its overall role, the terms would most likely be:
Covering (epithelium)
Support (connective)
Movement (muscle)
Control (nervous)
However, these terms only reflect only a tiny fraction of the functions that each of these tissues perform.

4. 1. Epithelial Tissues Found in different areas Body coverings
Body linings
Glandular tissue (forms glands in body)
Functions
Protection
Absorption
Filtration
Secretion

5. Special Characteristics of Epithelium:
Cells fit closely together (except for glandular) to form connective sheets
Tissue layer always has one free surface. This so called “apical surface” is exposed to the body’s exterior or to the cavity of an internal organ.
The lower surface of epithelium is bound by a basement membrane (a structure less material secreted by cells)
Avascular (have no blood supply) so they depend on diffusion from the capillaries in the underlying connective tissue for food and oxygen
Regenerate easily if well nourished
Pg. 86!!! Read to kids from here…extra info

6. Classification of Epithelium
1. Number of cell layers
Simple – one layer
Stratified – more than one layer
Figure 3.17a

7. Classification of Epithelium
2. Shape of cells
Squamous – flattened (like fish scales)
Cuboidal – cube-shaped (like dice)
Columnar – column-like (like columns…duh)
Figure 3.17b

8. Simple or Stratified… Simple Stratified
One layer of cells
Most concerned with absorption, secretion, and filtration
Because they are usually very thin, protection is not one of their specialties
Consist of two or more cell layers
More durable than the simple epithelia
Function primarily to protect

9. Simple Epithelium 1. Simple squamous Single layer of flat cells
Usually forms membranes where filtration or exchange of substances by rapid diffusion occurs.
Lines body cavities
Lines lungs and capillaries
It is in the air sacs of the lungs, where oxygen and carbon dioxide are exchanged and it forms the walls of capillaries, where nutrients and gases pass between the tissue cells and the blood in the capillaries.
Figure 3.18a

10. Simple Epithelium 2. Simple cuboidal Single layer of cube-like cells
Common in glands and their ducts
Forms walls of kidney tubules
Covers the ovaries
Figure 3.18b

11. Simple Epithelium 3. Simple columnar Single layer of tall cells
Often includes goblet cells, which produce mucus
Lines the entire digestive tract from the stomach to the anus
Figure 3.18c

12. Simple Epithelium 4. Pseudostratified
Single layer, but some cells are shorter than others
Often looks like a double cell layer (false…hence the name pseudo)
Sometimes ciliated, such as in the respiratory tract
May function in absorption or secretion
Rest on a basement membrane like the others, but because some of its cells are shorter than others, and their nuclei appear at different heights above the basement membrane…as a result, this epithelium give the false (pseudo) impression that it is stratified.
Figure 3.18d

13. Stratified Epithelium
1. Stratified squamous
Cells at the free edge are flattened but closer to the basement membrane, are cuboidal or columnar
Found as a protective covering where friction/abuse is common
Locations
Skin
Mouth
Esophagus
Figure 3.18e

14. Stratified Epithelium
2. Stratified cuboidal
Two layers of cuboidal cells
3. Stratified columnar
Surface cells are columnar, cells underneath vary in size and shape
Stratified cuboidal and columnar
Rare in human body
Found mainly in ducts of large glands

15. Stratified Epithelium
4. Transitional epithelium
Shape of cells depends upon the amount of stretching (near basement: typically columnar or cuboidal, at surface: varies)
Lines organs of the urinary system like the bladder, ureters, and part of the urethra where considerable amounts of stretching occur.
When the organ is not stretched, the membrane is many layered and the superficial cells are rounded and domelike. When the organ is distended with urine, the epithelium thins, and the surface cells flatten and become squamous-like. This ability of transitional cells to slide past one another and change their shape (undergo “transitions”) allows the ureter wall to stretch as a greater volume of urine flows through that tubelike organ. In the bladder, it allows more urine to be stored.
Figure 3.18f

16. Glandular Epithelium
Gland – one or more cells that secretes a particular product (secretion)
Two major gland types develop from epithelial sheets:
1. Endocrine gland
Ductless (hormones diffuse directly into the blood vessels that weave through the glands)
Secretions are all hormones
Examples of endocrine glands: thyroid, adrenals, and pituitary
2. Exocrine gland
Empty through ducts to the epithelial surface
Include sweat and oil glands, and liver and pancreas
Are both internal and external

17. Connective Tissue Found everywhere in the body & connects body parts
Includes the most abundant and widely distributed tissues
Functions
Binds body tissues together
Supports the body
Provides protection

18. Connective Tissue Characteristics:
Variations in blood supply
Some connective tissue types are well vascularized (good blood supply)
Some have poor blood supply or are avascular like tendons and cartilages (these things heal slowly)
Extracellular matrix
Connective tissues are made up of many different types of cells plus varying amounts of non-living material that surrounds living cells (called the extracellular matrix)

19. Extracellular Matrix. Makes connective tissue different from
Extracellular Matrix Makes connective tissue different from any other tissue.
Two main elements
Ground substance – mostly water along with adhesion proteins and polysaccharide molecules
Fibers
Produced by the cells
Three types
Collagen fibers
Elastic fibers
Reticular fibers

20. Extracellular Matrix Continued:
Allows connective tissue to
form a soft packaging tissue around other organs,
to bear weight,
and to withstand stretching and other abuses, such as abrasion
that no other tissue could endure.

21. Connective Tissue Types:
Bone (osseous tissue)
Composed of:
Bone cells in lacunae (cavities)
Surrounded by a hard matrix of calcium salts
Large numbers of collagen fibers
Because of its rocklike hardness, bone is used to protect and support the body
Figure 3.19a

22. Connective Tissue Types:
Hyaline cartilage
Most common cartilage (cartilage is found only in a few places in the body…is less hard and more flexible than bone.)
Composed of:
Abundant collagen fibers
Rubbery matrix
Blue-white appearance
Entire fetal skeleton is hyaline cartilage (turns to bone by birth)!
Also forms the supporting structure of the larynx (voicebox), attaches ribs to the breastbone, and covers the ends of bones where they form joints.
Figure 3.19b

23. Connective Tissue Types:
Elastic cartilage
Provides elasticity
Example: supports the external ear

24. Connective Tissue Types:
Fibrocartilage
Highly compressible
Example: forms cushion-like discs between vertebrae
Figure 3.19c

25. Connective Tissue Types:
Dense connective tissue
Main matrix element is collagen fibers
Cells are fibroblasts (fiber forming cells)
Forms strong ropelike structures (like the examples listed below)
Examples
Tendon – attach muscle to bone
Ligaments – attach bone to bone
Figure 3.19d

26. Connective Tissue Types:
Areolar connective tissue
Most widely distributed connective tissue
Soft, pliable “cobwebby” tissue that cushions and protects the body organs
Helps hold internal organs together and in their proper positions
Contains all fiber types
Can soak up excess fluid
Can soak up excess fluid when a body region is inflamed like a sponge. Then the area swells and turns red (called edema). Many types of phagocytes wander through this tissue, scavenging for bacteria, dead cells, and other debris, which they destroy!
Figure 3.19e

27. Connective Tissue Types:
Adipose tissue: Commonly called fat!
Matrix is an areolar tissue in which fat cells predominate
Many cells contain large lipid deposits
Functions
Insulates the body
Protects some organs
Serves as a site of fuel storage
Adipose tissue is found right beneath the skin where it insulates the body and protects it from extremes of both heat and cold. Kidneys are surrounded by a capsule of fat, and adipose tissue cushions the eyeballs in their sockets. There are also fat “depots” in the body, such as the hips and breasts, where fat is stored and available for fuel if needed.
Figure 3.19f

28. Connective Tissue Types:
Reticular connective tissue
Delicate network of interwoven fibers
Forms stroma (internal supporting network) of lymphoid organs
Lymph nodes
Spleen
Bone marrow
Figure 3.19g

29. Connective Tissue Types:
Blood (vascular tissue)
Blood cells surrounded by fluid matrix (called plasma)
Fibers are visible during clotting
Functions as the transport vehicle for the cardiovascular system, carrying nutrients, wastes, respiratory gases, and many other substances throughout the body.
Figure 3.19h

30. Muscle Tissue Skeletal muscle Cardiac muscle Smooth muscle
Function is to produce movement
Three types
Skeletal muscle
Cardiac muscle
Smooth muscle

31. Muscle Tissue Types: 1. Skeletal muscle Can be controlled voluntarily
Form the muscular system
Cells attach to connective tissue
Cells are striated (striped)
Cells have more than one nucleus
When the skeletal muscles contract, they pull on bones or skin. The result of their action is gross body movements or changes in our facial expressions.
Figure 3.20a

32. Muscle Tissue Types 2. Cardiac muscle Found only in the heart
Function is to pump blood (involuntary)
Cells attached to other cardiac muscle cells at intercalated disks (have gap junctions …remember this mean info can pass freely from cell to cell….)
Cells are striated
One nucleus per cell
Under involuntary control
Figure 3.20b

33. Muscle Tissue Types 3. Smooth muscle AKA: visceral muscle
Involuntary muscle
Surrounds hollow organs
Spindle-shaped (pointed at each end)
Attached to other smooth muscle cells
No visible striations (hence the name smooth)
One nucleus per cell
Smooth muscle is found in the wall so hollow organs such as the stomach, bladder, uterus, and blood vessels. As smooth muscle contracts, the cavity of an organ alternately becomes smaller (constricts on smoothe muscle contraction_ or enlarges (dilates on smooth muscle relaxation) so that substances are propelled through the organ along a specific pathway. Smooth muscle contracts much more slowly than the other two muscle types. Peristalsis, a wafelike motion that keeps food moving through the small intestine, is typical of its activity.
Figure 3.20c

34. Nervous Tissue Neurons and nerve support cells
Function is to send impulses to other areas of the body
Irritability
Conductivity
All neurons receive and conduct electrochemical impulses from one part of the body to another; thus irritability and conductivity are their two major functional characteristics. The structure of neurons is unique….their cytoplasm is drawn out into long processes (extensions), as much as 3 feet or more in the leg, which allows a single neuron to conduct an impulse over long distances in the body. Neurons, along with a special group of supporting cells that insulate, support, and protect the delicate neurons, make up the structures of the nervous system-the brain, spinal cord, and nerves.
Figure 3.21

35. Tissue Repair (Wound Healing)
Tissue repair occurs in two major ways…
1. Regeneration
Replacement of destroyed tissue by the same kind of cells
2. Fibrosis
Repair by dense fibrous connective tissue (scar tissue is formed)
Determination of method
Type of tissue damaged
Severity of the injury

36. Tissue injury sets a series of events into motion…
Capillaries become very permeable
Introduce clotting proteins
Wall off injured area
Formation of granulation tissue
Regeneration of surface epithelium
Be prepared to read pg. 98 while the kids write here!!!

37. 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
Read about Homeostatic Imbalance on pg. 98 and make notes….