AP Lecture Ch 5
Page 1: Copyright Information
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Reference to separate FlexArt PowerPoint slides for figures and tables.
Page 2: Overview of Histology
Introduction
The human body contains approximately 50 trillion cells of around 200 different types.
Tissues are classified into four broad categories:
Epithelial tissue
Connective tissue
Nervous tissue
Muscular tissue
An organ is defined as a structure with distinct boundaries composed of two or more tissue types.
Histology is the study of tissues and their organization into organs.
Page 3: Embryonic Tissues
Primary Germ Layers
Ectoderm: Develops into the epidermis and nervous system.
Endoderm: Forms the mucous membranes lining the digestive and respiratory tracts and various glands.
Mesoderm: Forms a gelatinous substance called mesenchyme, which gives rise to muscle, bone, and blood.
Page 4: Tissue Sections
Types of Tissue Sections
Longitudinal section (l.s.): Cuts along the long direction of the organ.
Cross section (c.s. or x.s.): Cuts perpendicular to the length of the organ.
Oblique section: Cuts at an angle between cross and longitudinal sections.
Page 5: Interpreting Tissue Sections
Smear: Rubbing tissue across a slide (e.g., spinal cord, blood).
Spread: Placing loose, cobweb-like tissues on a slide (e.g., areolar tissue).
Page 6: Epithelial Tissue Characteristics
Composed of a flat sheet of closely adhering cells.
Can be one or more cells thick.
Upper surface usually exposed to the exterior or an internal body space.
Serves to cover body surfaces and line cavities of organs.
Page 7: Epithelial Tissue Characteristics (Continued)
Makes up most glands.
Extracellular materials in epithelium are minimal and often invisible under light microscopy.
Epithelia lack blood vessels and rely on underlying connective tissues for nourishment and waste removal.
Page 8: Basement Membrane
Basement membrane: Structure separating epithelium from connective tissue.
Contains collagen, laminin, fibronectin, and heparan sulfate for adhesion.
Functions to anchor epithelium to connective tissue.
Basal surface: Faces the basement membrane.
Apical surface: Faces away from the basement membrane.
Page 9: Types of Epithelial Tissue
Simple Epithelium: One layer of cells, with all cells touching the basement membrane.
Stratified Epithelium: More than one layer, named by the shape of surface cells (apical).
Cell shapes include squamous, cuboidal, and columnar.
Page 10: Simple Epithelia Types
Four Types of Simple Epithelia:
Simple Squamous: Thin, scaly cells.
Simple Cuboidal: Round or square cells.
Simple Columnar: Tall, narrow cells.
Page 11: Pseudostratified Columnar Epithelium
Pseudostratified Columnar: Appears layered but is a single layer; not all cells reach the free surface.
Contains goblet cells for mucus secretion.
Page 12: Simple Squamous Epithelium
Structure: Single layer of thin cells.
Function: Allows rapid diffusion or transport; secretes serous fluid.
Locations: Alveoli, glomeruli, endothelium, and serosa.
Page 13: Simple Cuboidal Epithelium
Characteristics: Single layer of square/round cells.
Function: Absorption and secretion; mucus production.
Locations include liver, thyroid, and kidney tubules.
Page 14: Simple Columnar Epithelium
Structure: Tall, narrow cells with oval nuclei.
Function: Secretion and absorption; may have microvilli and goblet cells.
Located in the lining of the GI tract and uterus.
Page 15: Pseudostratified Epithelium Description
Structure: Appears multilayered with cilia and goblet cells.
Function: Secretes and propels mucus; found in the respiratory tract.
Page 16: Stratified Epithelia Overview
Composed of 2 to 20+ layers of cells; only the deepest layer attaches to the basement membrane.
Named based on the shape of surface cells:
Stratified squamous
Stratified cuboidal
Stratified columnar (rare)
Transitional epithelium.
Page 17: Stratified Squamous Epithelia
Characteristics: Deepest layer undergoes mitosis, daughter cells push upward and become flat.
Types: Keratinized (resists abrasion, found on skin) and Nonkeratinized (found in the mouth, esophagus).
Page 18: Keratinized Stratified Squamous
Structure: Multiple layers with flattening cells towards the surface.
Function: Resists abrasion; retards water loss.
Found in palms and soles.
Page 19: Nonkeratinized Stratified Squamous
Structure: Similar to keratinized but lacks the surface layer of dead cells.
Locations: Tongue, oral mucosa, esophagus, vagina.
Page 20: Stratified Cuboidal Epithelium
Structure: Two or more layers with surface cells that are square or round.
Function: Secretes sweat; involved in reproduction.
Locations: Sweat glands and ovarian follicles.
Page 21: Transitional Epithelium
Structure: Surface cells that change from round to flat when stretched.
Function: Allows filling of the urinary tract.
Found in ureters and bladder.
Page 22: Overview of Connective Tissue
Definition: Type of tissue where cells occupy less space than the extracellular material.
Function: Binds organs, supports, and protects organs; not all cells are in direct contact with each other, separated by material.
Highly vascular, abundant, and histologically variable.
Page 23: Functions of Connective Tissue
Binding organs (tendons, ligaments).
Support (bones, cartilage).
Protection (cranium, ribs, sternum).
Immune protection (white blood cells).
Storage (fat, calcium, phosphorus).
Heat production (brown fat in infants).
Transport (blood).
Page 24: Fibrous Connective Tissue
Cell Types:
Fibroblasts: Produce fibers and ground substance.
Macrophages: Phagocytize material and activate immunity.
Leukocytes: White blood cells (e.g., neutrophils, lymphocytes).
Mast Cells: Secrete heparin (inhibits clotting) and histamine (dilates blood vessels).
Adipocytes: Store fat.
Page 25: Fibers in Connective Tissue
Types of Fibers:
Collagenous fibers: Tough and resist stretching.
Reticular fibers: Thin fibers form framework for organs.
Elastic fibers: Provide stretch and recoil.
Page 26: Types of Fibrous Connective Tissue
Loose Connective Tissue: Gel-like ground substance; includes areolar and reticular tissue.
Dense Connective Tissue: Fibers fill spaces, includes regular and irregular types.
Page 27: Areolar Tissue Characteristics
Structure: Loosely organized fibers and abundant blood vessels.
Function: Surrounds blood vessels/nerves; underlies epithelium, providing nutrition and immune support.
Page 28: Areolar Tissue Description
Location: Underlies all epithelia, serous membranes, and pathways for vessels.
Page 29: Reticular Tissue Description
Structure: Mesh of reticular fibers supporting lymphatic organs.
Locations: Found in lymph nodes, spleen, thymus, and bone marrow.
Page 30: Dense Regular Connective Tissue
Characteristics: Densely packed, parallel collagen fibers.
Function: Provides strength; connects muscles to bones (tendons) and holds bones together (ligaments).
Page 31: Dense Irregular Connective Tissue
Structure: Packed, randomly arranged collagen fibers; few visible cells.
Function: Withstands unpredictable stresses, found in deeper skin layers and organ capsules.
Page 32: Adipose Tissue Overview
Definition: Tissue dominated by adipocytes; stores energy as fat.
Characteristics: Stable number of adipocytes with continuous recycling of triglycerides.
Page 33: Functions of Adipose Tissue
Provides thermal insulation.
Cushions organs such as kidneys and eyeballs.
Contributes to body contours, especially in females.
Page 34: Adipocyte Characteristics
Structure: Empty-looking cells with thin margins, nucleus pressed against membrane.
Functions: Energy storage, insulation, cushioning.
Page 35: Cartilage Overview
Definition: Supportive connective tissue with a flexible matrix.
Function: Gives shape to various structures; chondroblasts produce matrix.
Page 36: Cartilage Characteristics
Lacks blood vessels; nutrients diffuse through matrix, leading to slow healing.
Types include hyaline cartilage, fibrocartilage, and elastic cartilage.
Page 37: Hyaline Cartilage
Structure: Glassy appearance due to fine collagen fibers.
Function: Eases joint movement, supports airway, fetal skeleton.
Page 38: Elastic Cartilage
Function: Provides flexible support, found in the external ear and epiglottis.
Page 39: Fibrocartilage
Function: Resists compression and absorbs shock; found in pubic symphysis and intervertebral discs.
Page 40: Bone Overview
Definition: Bone as an organ and a type of osseous tissue.
Types: Spongy bone (with trabeculae) and compact bone.
Page 41: Compact Bone Structure
Comprised of cylindrical units called osteons.
Features include Haversian canals for blood vessels and nerves.
Page 42: Bone Cell Types
Osteocytes: Mature bone cells in lacunae; connected through canaliculi.
Periosteum: Covers bone.
Page 43: Blood Overview
Definition: Fluid connective tissue that transports cells and dissolved matter.
Components: Plasma, erythrocytes, leukocytes, and platelets.
Page 44: Excitable Tissues Overview
Definition: Tissues that respond to stimuli (nervous and muscular).
Excitability: Basis of the function; changes in membrane potential lead to signal transmission (nerves) and contractions (muscles).
Page 45: Nervous Tissue Overview
Function: Specializes in communication through electrical signals.
Composed of neurons and neuroglia.
Page 46: Neuron Structure
Parts of Neuron:
Neurosoma: Cell body with nucleus.
Dendrites: Receive signals.
Axon: Sends outgoing signals.
Page 47: Muscular Tissue Overview
Function: Specialized cells that contract to produce movement.
Types: Skeletal, cardiac, and smooth muscle.
Page 48: Skeletal Muscle Characteristics
Long cells called muscle fibers; voluntary control.
Striations present.
Page 49: Cardiac Muscle Characteristics
Located in the heart; involuntary control.
Features intercalated discs; shorter and branched cells.
Page 50: Smooth Muscle Characteristics
Lacks striations; involuntary control.
Forms layers in various organs.
Page 51: Cell Junctions
Definition: Connections between cells, providing resistance to stress and facilitating communication.
Page 52: Tight Junctions
Zones that bind adjacent cells, preventing passage of substances between.
Page 53: Desmosomes
Cell junctions that hold cells together to resist mechanical stress.
Hemidesmosomes anchor epithelial cells to the basement membrane.
Page 54: Gap Junctions
Formed by connexons, allowing substances to pass between cells.
Page 55: Gland Overview
Defined as cells or organs that secrete substances.
Comprised of epithelial tissue supported by connective tissue.
Page 56: Exocrine vs. Endocrine Glands
Exocrine: Have ducts, secrete onto surfaces (e.g., sweat glands).
Endocrine: Ductless, secrete hormones directly into blood (e.g., thyroid glands).
Page 57: Types of Secretions
Serous Glands: Produce watery secretions.
Mucous Glands: Produce mucin, which forms mucus when mixed with water.
Page 58: Membranes
Line body cavities and cover organs.
Types:
Cutaneous membrane: Skin.
Mucous membrane: Lines openings to the external environment.
Serous membrane: Covers organs in cavities.
Page 59: Mucous and Serous Membranes
Mucous: Composed of epithelial cells and lamina propria; lines digestive and respiratory tracts.
Serous: Simple squamous epithelium on areolar tissue; produces serous fluid.
Page 60: Stem Cells Overview
Definition: Undifferentiated cells with potential to become specialized cells.
Types: Embryonic and adult stem cells.
Page 61: Tissue Repair Mechanisms
Regeneration: Replacement with the same type of cells.
Fibrosis: Replacement with scar tissue, does not restore normal function.
Page 62: Tissue Repair Process
Phases:
Bleeding, clotting, and recruitment of cells for healing.
Page 63: Tissue Degeneration and Death
Atrophy: Shrinkage of tissue from loss of cells.
Necrosis: Pathological tissue death.
Page 64: Apoptosis
Programmed cell death; occurs naturally as part of development and tissue homeostasis.
Page 65: Tissue Engineering Overview
Creation of artificial tissues/organs.
Techniques involve scaffolding with living cells.
Page 66: Tissue Engineering Examples
Current advancements in skin grafts, heart valves, and urinary bladders.
Page 67: Stem Cell Controversy
Ethical concerns surrounding the use of embryonic stem cells versus adult stem cells .
Page 68: Exam Questions
Questions added for assessment purposes.
Page 69: Exam Questions (Continued)
Additional assessment questions.