AP Lecture Ch 5

Page 1: Copyright Information

• Copyright © The McGraw-Hill Companies, Inc.

• Permission required for reproduction or display.

• 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.