Chapter 4: The Tissue Level of Organization

1
Chapter 4 The Tissue Level of Organization
2
What are the four tissues of the body?
3

• Tissues are collections of cells and cell
  products that perform specific, limited functions
• Histology
• 4 tissue types form all the structures of the
  human body
• epithelial, connective, muscle, and neural

4
Epithelial Tissues

• Epithelia
• layers of cells covering internal or external
  surfaces
• Glands
• structures that produce secretions

5
What are the special structures and functions of
epithelial tissues?
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Characteristics of Epithelia

• Cellularity
• Polarity
• Attachment (basal lamina)
• Avascularity
• Regeneration

7
Functions of Epithelial Tissue

• Provide physical protection
• Control permeability
• Provide sensation
• Produce specialized secretions (glandular
  epithelium)
• Microvilli or cilia

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Maintaining Epithelia Integrity

• Intercellular connections
• Attachment to the basal lamina
• Epithelial maintenance and repair

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Intercellular Connections

• Support and communication

Figure 42a
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Large Connections

• CAMs (cell adhesion molecules)
• transmembrane proteins
• Intercellular cement
• glycoproteins
• Hyaluronan (hyaluronic acid)

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Cell Junctions

• Form bonds with other cells or extracellular
  material
• tight junctions
• gap junctions
• desmosomes

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Tight Junctions

• Interlocking membrane proteins
• Prevents passage of water and
  solutes

Figure 42b
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Gap Junctions

• Allow rapid communications
• Held together by channel proteins (connexons)
• Allow ions to pass

Figure 42c
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Desmosomes

• CAMs and intercellular cement
• Allow bending and twisting without separation

Figure 42d
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Attachment to Basal Lamina

• Epithelial cells hold onto each other and are
  connected to the rest of the body
• Inner surface is connected to a 2-part basal
  lamina
• Lamina lucidia
• Lamina densa

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Maintenance Repair

• An epithelium must continuously repair and renew
  itself
• Function of stem cells (germinative cells)
  located near basement membrane

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Classes of Epithelia

• Based on shape and layers

Table 41
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Layers

• Simple epithelium
• single layer of cells
• Stratified epithelium
• several layers of cells
• Pseudo-stratified epithelium
• single layer of cells that appears stratified

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Cell Shape

• Squamous epithelia
• flat shaped
• Cuboidal epithelia
• square shaped
• Columnar epithelia
• tall shaped

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Glandular Epithelia

• Endocrine
• Release hormones
• into interstitial fluid
• no ducts
• Exocrine
• Produce secretions
• onto epithelial surfaces
• through ducts

Figure 46
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• Exocrine glands can be classified by
• Mode of secretion
• Type of secretion
• Structure of gland
• Unicellular or multi-cellular
• Simple vs. compound

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Modes of Secretion

• Merocrine secretion

Figure 46a
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Modes of Secretion

• Apocrine secretion

Figure 46b
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Modes of Secretion

• Holocrine secretion

Figure 46c
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Types of Secretions

• Serous
• Mucus
• Mixed

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

• Specialized cells
• Matrix
• Solid extracellular protein fibers
• Fluid extracellular ground substance

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Functions of Connective Tissues

• Connect epithelium to the rest of the body (basal
  lamina)
• Provide structure (bone)
• Transport materials (blood)
• Protection
• Store energy (fat)
• Defense

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Classification of Connective Tissues

• Connective tissue proper
• connect and protect
• Fluid connective tissues
• transport
• Supportive connective tissues
• structural strength

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Connective Tissue Proper
Figure 48
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8 Cell Types of Connective Tissue Proper

• Fibroblasts
• Macrophages
• Adipocytes
• Mesenchymal cells

• Melanocytes
• Mast cells
• Lymphocytes
• Microphages

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Fibers in Connective Tissue Proper

• Collagen fibers
• most common strong and flexible
• tendons and ligaments
• Elastic fibers
• contain elastin
• Reticular fibers
• strong and flexible
• resists force in many directions

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Ground Substance

• In connective tissue proper and ground substance
  
• is clear, colorless, and viscous
• fills spaces between cells and slows pathogens

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Categories of Connective Tissue Proper

• Loose connective tissue
• more ground substance, less fibers
• Areolar adipose reticular
• Dense connective tissue
• more fibers, less ground substance
• e.g., tendons

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Dense Connective Tissues

• Connective tissues proper, tightly packed with
  high numbers of collagen or elastic fibers
• dense regular connective tissue
• dense irregular connective tissue

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Fluid Connective Tissues

• Fluid connective tissues
• blood and lymph
• watery matrix of dissolved proteins
• carry specific cell types (formed elements)

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Formed Elements of Blood
Figure 412
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Supportive Connective Tissues

• Support soft tissues and body weight
• cartilage
• for shock absorption and protection
• Chondrocytes
• Hyaline cartilage Elastic cartilage
  Fibrocartilage
• Bone (osseous tissue)
• calcified (made rigid by calcium salts, minerals)
• for weight support
• Osteocytes

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• How do epithelial and
• connective tissues combine to
• form 4 types of membranes?

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Membranes

• Membranes
• are physical barriers
• that line or cover portions of the body
• Consist of
• an epithelium
• supported by connective tissues

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4 Types of Membranes

• Mucous- line passageways that have external
  connections
• Serous - Line cavities not open to the outside
• Pleural Peritoneum Pericardium
• Cutaneous - skin
• Synovial - joint cavities

Figure 416
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What are the structures and functions of the
three types of muscle tissue?
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Muscle Tissue

• Produces all body movement
• Specialized for contraction
• Actin and myosin fibers
• Muscle fibers and satellite cells

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3 Types of Muscle Tissue

• Skeletal muscle
• Striated, voluntary, and multinucleated
• Cardiac muscle
• Striated, involuntary, and single nucleus
• Smooth muscle
• Nonstriated, involuntary, and single nucleus

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What is the basic structure and role of neural
tissue?
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Neural Tissue

• Also called nervous or nerve tissue
• specialized for conducting electrical impulses
• rapidly senses internal or external environment
• process information and controls responses

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Central Nervous System

• Neural tissue is concentrated in the central
  nervous system
• brain
• spinal cord

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2 Kinds of Neural Cells

• Neurons
• nerve cells
• perform electrical communication
• Neuroglia
• support cells
• repair and supply nutrients to neurons

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The Neuron
Figure 419
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SUMMARY

• Organization of specialized cells into tissues
• epithelial tissue
• connective tissue
• muscular tissue
• nervous tissue

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• Division of epithelial tissues into epithelia and
  glands
• epithelia as avascular barriers for protection
• glands as secretory structures

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• Attachments of epithelia to other cells and
  underlying tissues
• polarity (apical surface and basal lamina)
• cell adhesion molecules (CAMs)
• cell junctions (tight junctions, gap junctions
  and desmosomes)

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• Classification of epithelial cells
• by number of cell layers (simple or stratified)
• by shape of cells (squamous, columnar or cuboidal)

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• Classification of epithelial glands
• by method of secretion (exocrine or endocrine)
• by type of secretions (merocrine, apocrine,
  holocrine)

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• The functions of connective tissues
• structure
• transport
• protection
• support
• connections
• energy storage

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• The structure of connective tissues
• matrix
• ground substance
• protein fibers

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• The classification of connective tissues
• connective tissue proper (cell types, fiber
  types, and embryonic connective tissues)
• fluid connective tissues (blood and lymph, fluid
  transport systems)
• supporting connective tissues (cartilage and bone)

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• The 4 types of membranes that cover and protect
  organs
• mucous membranes (lamina propria)
• serous membranes (transudate)
• cutaneous membrane (skin)
• synovial membrane (encapsulating joints)

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• The 3 types of muscle tissues (skeletal, cardiac,
  and smooth)
• The classification of muscle tissues by
  striation, nucleation, and voluntary control

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• The 2 types of cells in neural tissue
• neurons and neuroglia
• The parts of a neuron (nerve cell)
• cell body, dendrites, and axon (nerve fiber)