1. CH 4: Tissues

2. Tissues
Tissues are groups of cells that are similar in structure and function.
Tissues can be solid, semi-solid or liquid.
Histology is the study of tissues.
There are 4 main types of tissues in the human body:
Epithelial
Connective
Muscular
Nervous

3. Epithelial Tissue (Epithelium)
Covers body surfaces and lines cavities, hollow organs and tubes. It also forms glands.
Cells are closely packed and arranged in sheets of either single or multiple layers.
Bottom surface of epithelium is attached to the basement membrane- fibers that are located between the epithelium and the connective tissue below it.

4. Epithelium continued…..
Avascular- without blood vessels. Epithelium gets nutrients from the adjacent connective tissue.
Has a nerve supply.
Is constantly being regenerated because it suffers so much wear and tear.
There are 2 main types of epithelial tissue:
Covering/Lining epithelium
Glandular epithelium

6. Covering/Lining Epithelium
Outer covering of the skin and some internal organs.
Inner lining of blood vessels, ducts, and body cavities.
Interior of the digestive, respiratory, reproductive and urinary systems.

7. Glandular Epithelium Consists of glands that secrete substances.
Glands are either endocrine or exocrine.
Endocrine- Secrete hormones that enter the fluid around the cells (interstitial) and eventually the bloodstream (Ex. thyroid)
Exocrine- Secrete substances into ducts that empty onto the surface of a covering/lining epithelium (Ex. Sweat gland)

8. Epithelial Tissue Classification
Epithelial tissue is classified based on the number of cell layers present and the shape of the cells of the tissue.
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9. Number of Layers Simple- Stratified- one layer 2 or more layers
usually involved in absorption and/or diffusion
Stratified-
2 or more layers
Protects underlying tissues from wear and tear

10. Number of Layers Continued..
Pseudostratified
Looks like many layers because not all cells reach the surface and the nuclei lie at different levels

11. Cell Shape Squamous Thin and flat and attach to each other like tiles
Easily allow substances to pass through
Cuboidal
Shaped like cubes
Function in secretion or absorption

12. Cell Shape Continued… Columnar taller than wide
protect underlying tissues
Transitional
change shape due to stretching or movement of body parts

13. Other modifications
Cilia- Tiny hairs that move substances around outside the cell
Microvilli- Folds that increase surface area for absorption
Goblet cells- embedded in between epithelium and secrete mucus for lubrication or to trap particles

14. Simple Squamous
A single layer of tightly packed thin, flat, irregularly shaped cells
Location:
Lines the heart, blood vessels, and lymphatic vessels
Forms the peritoneum, pericardium and pleural linings
Found in the air sacs of lungs (alveoli)
Function:
Allows for easy diffusion of gases and blood components

15. Simple Squamous – Top View – found in the walls of capillaries and alveoli of lungs

17. Simple Cuboidal A single layer of tightly packed cube shaped cells.
Location:
Lines kidney tubules, ducts of glands, and secreting parts of glands
Covers the surface of the ovary
Function:
Secretion and absorption

18. Simple Cuboidal Epithelial Tissue – this is of ducts of the kidney

21. Simple Columnar A single layer of tightly packed rectangular cells
Can be non-ciliated or ciliated
Goblet cells are modified columnar cells that secrete mucus
Non-ciliated have microvilli on the surface of the cells
Non-ciliated Location:
Lines the gastrointestinal tract (from stomach to anus), ducts of many glands, and gall bladder

22. Simple Columnar Continued…
Non-ciliated Function:
Secretion and absorption
Ciliated Location:
Lines tubes of the respiratory tract, fallopian tubes, uterus, and ventricles of the brain
Ciliated Function:
The cilia beat in unison to move substances outside the cell like mucus and egg cells.

23. Simple Columnar Non-Ciliated Epithelial Tissue - This is a cross section through the small intestine – for absorption – microvilli on surface of cells

26. Pseudostratified Columnar
A single layer of tightly packed columnar cells that appear to be multi-layered
Location:
Ciliated- Lines respiratory tract
Non-ciliated- Male urethra
Function:
Ciliated- moves materials across the apical surface of a tissue.
Non-ciliated- Absorb and protect

28. Stratified Squamous
Multiple layers of tightly packed squamous epithelial cells.
Location:
Areas that are subject to much “wear and tear”.
Upper layers are designed to be shed and replaced.
Function:
Protection

30. Stratified Cuboidal Two layers of cube shaped epithelial cells Rare
Location:
Lining the ducts of glands found in the esophagus
Function:
Moderate protection from the stomach acid that refluxes

32. Stratified Columnar Multiple layers of columnar epithelial cells Rare
Only the layer closest to the lumen (opening in a duct) is columnar in shape. The outer layers are somewhat squashed.
Location:
Lining the ducts of glands lining the esophagus
Function:
Moderate protection from stomach acid that refluxes

34. Transitional Epithelial tissue that has a variable shape Location:
Can stretch and relax multiple times without being damaged
Location:
Lines the urinary bladder
Function:
Protection

36. Let’s Practice
For the following, indicate the type of epithelial tissue and where you would find it.

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51. Connective Tissue
The most abundant and widely distributed type of tissue in the whole body.
General characteristics:
With the exception of 3 types, connective tissues have a great blood supply.
Reproduce quickly
Classified as being “connective” because at least 50% of the tissue is non-living.

52. Connective Tissue continued….
Function:
Designed to bind tissues together
Helps protect the body
Store energy in the form of fat
Transport materials throughout the body (blood, lymph)
2 main components of connective tissue:
Matrix
Cells

53. Matrix of Connective Tissue
A base material that contains protein fibers and is found between the cells of connective tissue.
Fibers are proteins found in the matrix that strengthen and support connective tissue.
Non-living
The structure of the matrix determines the characteristics of the connective tissue
Functions to support the cells of the connective tissue

54. Fibers in Connective Tissue
The properties of a connective tissue can change if the types/amounts of fibers in the matrix change.
Types of fibers:
Collagen- Strong and flexible and add strength to connective tissue
Elastic- Strong and add flexibility to connective tissue
Reticular- Strong and highly branching fibers that help form the framework of a connective tissue

56. Cells of Connective Tissue
Not all of the possible types are found in all connective tissues
Fibroblasts:
Make the fibers found in the matrix
Found in most connective tissues
Phagocytes:
Macrophages and neutrophils- Phagocytic cells that “eat and eliminate” foreign materials.

57. Cells of Connective Tissue continued…
Plasma cells:
Found in most connective tissues
Produce antibodies
Antibodies- Molecules that help protect us from foreign particles
Mast cells:
Found in all connective tissues
Release histamine
Histamine- Causes swelling because it signals for blood vessels to become more “leaky” and signals for blood to rush to an area

59. Cells of Connective Tissue continued…
Adipocytes:
Found in some connective tissues
Contain fat

60. Types of Connective Tissue
There are 6 types of mature connective tissue. They include: loose connective tissue, dense connective tissue, cartilage, bone tissue, blood tissue and lymph.

61. Loose Connective Tissue
Loosely arranged fibers in the matrix.
Areolar- Loose arrangements of collagen, elastic and reticular fibers present in the matrix
Location: Between the skin and muscle and holds the skin in place
Function: Binds structures together, provides strength (collagen), and provides flexibility (elastic)
Adipose- Lipids (fats) present in the matrix
Location: Below the skin and surrounding organs
Function: Stores fat, insulates against heat loss, and protects organs

64. Loose Connective Tissue
Reticular- Loose arrangements of reticular fibers and reticulocytes in the matrix
Function: Form the framework for larger organs (like the framework of a house)

66. Dense Connective Tissue
Large amounts of thick, dense fibers and fewer cells than loose connective tissue
Dense regular- Parallel bundles of collagen fibers present in the matrix
Connects muscle to bone (tendon) or bone to bone (ligament)
Can resist lots of force along the length of the fibers
A force against the fibers can tear them (torque)
Poor blood supply so it takes a long time to heal

68. Dense Connective Tissue
Dense irregular- Random arrangements of collagen fibers present in the matrix.
Good blood supply
Makes up the dermis (middle layer) of the skin
Resists pulling forces in multiple directions

70. Dense Connective Tissue
Elastic: Freely branching elastic fibers present in the matrix.
Good blood supply
Makes up the wall of an artery
Allows a hollow structure to expand and recoil freely
This keeps blood moving along in arteries

72. Cartilage
Consists of a dense network of collagen and elastic fibers in a semi-solid matrix
Poor blood supply
Chondrin- Gel-like protein found making up the matrix of cartilage tissue
Types of cartilage
Hyaline
Cartilage cells (chondrocytes) suspended in a chondrin matrix.
Acts as a shock absorber
Covers the ends of bones at a joint

74. Types of cartilage continued…
Fibrocartilage
Large bundles of collagen fibers and few chondrocytes suspended in a chondrin matrix
Forms the larger tendons of the body
Acts as a shock absorber
Elastic cartilage
Elastic fibers and few chondrocytes suspended in a chondrin matrix

77. Bone Characterized by a matrix composed of inorganic minerals.
Minerals are embedded in rings
Support and protect
Histology of bone will be explained later in the Bone unit

79. Blood Liquid connective tissue
Transports materials throughout the body
2 basic components:
Plasma-
55% of total blood
mostly water
supports the formed elements
Formed elements (cells)-
Erythrocytes- red blood cells- transport oxygen- outnumber white cells 700:1
Leukocytes- white blood cells- fight infection
Thrombocytes- platelets- cell fragments- help form blood clots

80. Lymph Liquid connective tissue
Located in lymphatic vessels- separate from blood vessels
No red blood cells nor platelets
Fights infection

82. Fluid Connective Tissue

83. Let’s Practice Connective Tissues

102. Muscle Tissue
Muscle tissue consists of cells that are highly specialized to generate force. This force, produces motion, maintains posture, and generates heat.
Muscle tissue cells have lots of mitochondria. Why?
There are 3 types of muscle tissue. They are skeletal muscle, smooth muscle and cardiac muscle.
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104. Skeletal Muscle
Skeletal muscle is named for its location. It is attached to bones of the skeleton.
Made of long cells called muscle fibers that attach to bones by connective tissue (tendon). Do you remember what kind of connective tissue? These cells are multinucleated.
Proteins within skeletal muscle cells are very organized creating striations (alternating light and dark bands).
In most cases, this type of muscle tissue is voluntary (consciously controlled). Can you think of a case when it is involuntary?

105. Skeletal Muscle

106. Smooth Muscle
Smooth muscle is located in the walls of hollow internal structures such as blood vessels, airways to the lungs, the stomach, intestines, and bladder.
It constricts blood vessels, physically breaks down and moves food and moves fluid through the body.
Smooth muscle tissue is not striated and involuntary
The cells of smooth muscle have 1 nucleus.

107. Smooth Muscle

108. Cardiac Muscle Cardiac muscle forms the bulk of the wall of the heart.
Cardiac tissue is striated and involuntary.
Cardiac muscle fibers are y-branched and have 1 nucleus.
Cardiac muscle fibers are attached end to end by thickened membranes called intercalated disks. These hold the fibers together during contractions.

109. Cardiac Muscle
intercalated disk
nucleus
striations

111. Skeletal Tissue

114. Smooth Muscle Tissue

115. Cardiac Muscle Tissue

117. Nervous Tissue
Nervous tissue functions to convert stimuli into nerve impulses (electricity) and conduct these impulses to other nerve cells, muscle fibers or glands.
The 2 types of nerve cells are neurons and neuroglia.
Neurons conduct nerve impulses and neuroglia do not.

118. Neuron structure

120. Nervous Tissue

122. ACT-UP

123. ACT - UP
The characteristics of tissue allow it to perform specific functions. Choose 5 different tissue types from this unit and answer the following for each:
Where can this tissue be found in the body?
What is/are the functions of this tissue?
What are 2 physical characteristics of this tissue?
How do both of the physical characteristics help the tissue perform its functions?