Chapter 4 Study Guide

1. Identifying Tissue Types

A. Epithelium

Characteristics:

- Cell Type: Epithelial cells are tightly packed, forming continuous layers. They have a basal lamina (part of the basement membrane) and apical surface. They can be classified based on shape and layering:

- Simple Epithelium: Single layer of cells.

- Stratified Epithelium: Multiple layers of cells.

- Pseudostratified Epithelium: Appears layered due to varied cell heights but is a single layer.

Special Features:

- Intercalated Disks: Not found in epithelial tissue; they are specific to cardiac muscle.

- Basement Membrane: A thin, fibrous extracellular matrix that supports epithelial cells and anchors them to underlying tissues.

Functions and Locations:

- Simple Squamous Epithelium:

- Function: Facilitates diffusion and filtration due to its thinness.

- Location: Lining of blood vessels (endothelium), alveoli in lungs, and glomeruli in kidneys.

- Stratified Squamous Epithelium:

- Function: Provides protection against abrasion and pathogens.

- Location: Epidermis of the skin, oral cavity, esophagus, and vagina.

- Simple Cuboidal Epithelium:

- Function: Secretion and absorption.

- Location: Kidney tubules, ducts of small glands, and ovary surface.

- Simple Columnar Epithelium:

- Function: Absorption and secretion; may include goblet cells that secrete mucus.

- Location: Lining of the digestive tract (stomach to rectum), uterine tubes.

- Pseudostratified Columnar Epithelium:

- Function: Secretion and movement of mucus (often ciliated).

- Location: Respiratory tract (trachea, bronchi).

Structure-Function Relationship:

- Simple Epithelium: Thin and permeable for efficient exchange processes.

- Stratified Epithelium: Multiple layers provide robust protection.

- Specialized Structures: Cilia and microvilli enhance absorption and movement.

### B. Connective Tissue

Characteristics:

- Cell Type: Various types such as fibroblasts (secrete matrix), adipocytes (store fat), macrophages (immune defense), and mast cells (involved in inflammation).

- Fiber Types:

- Collagen Fibers: Provide tensile strength.

- Elastic Fibers: Allow stretch and recoil.

- Reticular Fibers: Support delicate structures.

Special Features:

- Extracellular Matrix (ECM): Composed of ground substance (gel-like) and fibers; provides structural and biochemical support.

Functions and Locations:

- Loose Connective Tissue (Areolar Tissue):

- Function: Cushions and supports tissues and organs; facilitates nutrient exchange.

- Location: Beneath epithelial tissues, around organs.

- Dense Connective Tissue:

- Function: Provides strong attachment and support.

- Location:

- Dense Regular: Tendons and ligaments.

- Dense Irregular: Dermis of the skin, joint capsules.

- Cartilage:

- Function: Provides flexible support and reduces friction.

- Location:

- Hyaline Cartilage: Nose, trachea, and ends of long bones.

- Elastic Cartilage: Ear and epiglottis.

- Fibrocartilage: Intervertebral discs, menisci of knees.

- Bone (Osseous Tissue):

- Function: Provides structural support and protection; stores minerals.

- Location: Skeleton.

- Blood:

- Function: Transports nutrients, gases, wastes, and other substances.

- Location: Circulatory system (vessels).

Structure-Function Relationship:

- Loose Connective Tissue: Flexibility and support due to a loose arrangement of fibers.

- Dense Connective Tissue: High tensile strength for resistive support.

- Cartilage and Bone: Cartilage provides cushioning and flexibility; bone provides rigid support and protection.

### C. Muscle Tissue

Characteristics:

- Cell Type:

- Skeletal Muscle: Long, cylindrical cells, multi-nucleated, and striated.

- Cardiac Muscle: Branched cells, striated, with one or two nuclei, connected by intercalated disks.

- Smooth Muscle: Spindle-shaped cells, non-striated, with a single nucleus.

Special Features:

- Intercalated Disks: Found only in cardiac muscle, facilitating synchronized contractions.

Functions and Locations:

- Skeletal Muscle:

- Function: Voluntary movement, posture maintenance, heat production.

- Location: Attached to bones (e.g., biceps, quadriceps).

- Cardiac Muscle:

- Function: Involuntary rhythmic contractions of the heart.

- Location: Heart wall (myocardium).

- Smooth Muscle:

- Function: Involuntary contractions for movements within organs.

- Location: Walls of hollow organs (e.g., intestines, blood vessels).

Structure-Function Relationship:

- Skeletal Muscle: Striations and multiple nuclei facilitate rapid and strong voluntary contractions.

- Cardiac Muscle: Intercalated disks enable coordinated and rhythmic heart contractions.

- Smooth Muscle: Spindle shape allows for slow and sustained contractions in various organ systems.

### D. Nervous Tissue

Characteristics:

- Cell Type:

- Neurons: Specialized for transmitting electrical signals.

- Glial Cells: Support and protect neurons; include astrocytes, oligodendrocytes, microglia, and Schwann cells.

Special Features:

- Myelin Sheath: Produced by oligodendrocytes (CNS) and Schwann cells (PNS), insulating axons and speeding signal transmission.

Functions and Locations:

- Neurons:

- Function: Transmission of electrical impulses, processing information.

- Location: Brain, spinal cord, peripheral nerves.

- Glial Cells:

- Function: Support neurons, maintain homeostasis, and form myelin.

- Location: Throughout the central and peripheral nervous systems.

Structure-Function Relationship:

- Neurons: Long axons and numerous dendrites enable rapid communication over long distances.

- Glial Cells: Diverse functions in maintaining neuronal environment and providing support.

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## 2. Junctions in Epithelium

A. Tight Junctions:

- Structure: Composed of claudins and occludins that form a continuous seal around cells.

- Function: Prevents leakage of extracellular fluid between cells, maintaining a selective barrier.

- Location: Intestinal lining, bladder, and kidneys.

B. Anchoring Junctions:

- Structure: Includes desmosomes and hemidesmosomes.

- Desmosomes: Spot-like adhesions that use cadherins and intermediate filaments to link adjacent cells.

- Hemidesmosomes: Attach epithelial cells to the underlying basement membrane using integrins and intermediate filaments.

- Function: Provide mechanical strength and stability, resisting tensile forces.

- Location: Skin, cardiac muscle, and uterine cervix.

C. Gap Junctions:

- Structure: Connexons form channels that allow ions and small molecules to pass directly between cells.

- Function: Facilitates cell-to-cell communication and coordination, particularly important in cardiac and smooth muscle tissue.

- Location: Cardiac muscle, smooth muscle, and some epithelial tissues.

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## 3. Glands

A. Endocrine vs. Exocrine Glands:

- Endocrine Glands:

- Structure: Ductless; secrete hormones directly into the bloodstream or interstitial fluid.

- Function: Regulation of physiological processes (e.g., metabolism, growth).

- Examples: Thyroid gland (thyroxine), adrenal glands (adrenaline), pituitary gland (growth hormone).

- Exocrine Glands:

- Structure: Have ducts; secrete substances onto epithelial surfaces or into body cavities.

- Function: Localized secretion for digestion, lubrication, or protection.

- Examples: Sweat glands (sweat), salivary glands (saliva), pancreatic glands (digestive enzymes).

B. Unicellular vs. Multicellular Glands:

- Unicellular Glands:

- Structure: Single cell, such as goblet cells.

- Function: Secrete mucus.

- Location: Respiratory tract (trachea), digestive tract (intestines).

- Multicellular Glands:

- Structure: Composed of clusters of cells, forming more complex structures.

- Function: Diverse secretions, including enzymes, hormones, and other substances.

- Location:

- Simple Glands: Single, unbranched duct (e.g., gastric glands).

- Compound Glands: Branched ducts (e.g., salivary glands, pancreas).

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## 4. Membranes

A. Mucous Membranes:

- Structure: Epithelium (varies by location) over a connective tissue layer (lamina

propria).

- Function: Secretes mucus for lubrication and protection; often involved in absorption and secretion.

- Location: Lining of digestive tract (mouth to anus), respiratory tract (nasal cavity to bronchi), urogenital tract.

B. Serous Membranes:

- Structure: Simple squamous epithelium (mesothelium) over a thin connective tissue layer.

- Function: Produces serous fluid to reduce friction between organs.

- Location:

- Pleura: Surrounds lungs.

- Pericardium: Surrounds the heart.

- Peritoneum: Lines the abdominal cavity and covers abdominal organs.

C. Cutaneous Membranes:

- Structure: Stratified squamous epithelium (epidermis) over connective tissue (dermis).

- Function: Protection against mechanical damage, pathogens, and dehydration; involved in thermoregulation and sensation.

- Location: Skin.

D. Synovial Membranes:

- Structure: Connective tissue with synoviocytes producing synovial fluid.

- Function: Lubricates and nourishes cartilage in joints.

- Location: Joint cavities (e.g., knee, elbow).

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## 5. Tissue Regeneration

A. Tissues that Regenerate Quickly:

- Epithelial Tissue:

- Regeneration: High regenerative capacity due to rapid cell turnover.

- Examples: Skin (epidermis), intestinal lining (enterocytes).

- Connective Tissue:

- Regeneration: Varies; loose connective tissues regenerate faster than dense connective tissues.

- Examples: Adipose tissue, areolar tissue.

B. Tissues with Limited Regeneration:

- Cardiac Muscle:

- Regeneration: Limited; damaged cells are replaced by fibrous scar tissue.

- Implication: Poor recovery from myocardial infarction.

- Nervous Tissue:

- Regeneration: Limited; neurons have minimal capacity for regeneration.

- Examples: Damage to spinal cord or brain often results in permanent deficits.