Tissues

Overview of Tissue Science Histology ◦The study of tissues Four Basic Tissue Types ◦Epithelial ◦Connective ◦Muscular ◦Neural Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Overview of Tissue Science Tissues collections of cells and extracellular material perform a specific but limited range of functions the four tissue types, in varying combinations, form all of the structures of the human body Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Overview An Orientation to the Tissues of the Body Figure 4-1

Epithelial Tissue Epithelium ◦An avascular layer of cells that forms a barrier that covers internal or external surfaces Glands ◦Secretory structures derived from epithelia Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Epithelial Tissue Characteristics of Epithelia ◦Cells closely packed ◦Apical cells exposed to external or internal surface ◦Cells attached to basement membrane ◦Lack blood vessels ◦Cells continually replaced Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Epithelial Tissue Functions of Epithelia ◦Physical protection ◦Permeability control ◦Sensation trigger ◦Specialized secretions Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Epithelial Tissue Two Classes of Glandular Secretion ◦Exocrine secretion  Secretion onto a body surface ◦Endocrine secretion  Secretion (of hormones) into neighboring tissues and blood Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Epithelial Tissue Intercellular Connections ◦Cell adhesion molecules ◦Cell junctions  Tight junctions  Gap junctions  Desmosomes Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Epithelial Tissue Intercellular Connections Figure 4-2

Epithelial Tissue The Epithelial Surface ◦Microvilli  Abundant on transport cells  Dramatically increase surface area  Found in intestinal lining, kidney tubules ◦Cilia  Beat in coordinated fashion  Move fluid along surface  Found in airways, oviduct Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Epithelial Tissue The Surfaces of Epithelial Cells Figure 4-3

Epithelial Tissue The Basement Membrane ◦Noncellular meshwork anchors basal cells ◦Underlies all epithelia ◦Hemidesmosomes attach basal cells ◦Resists passage of large molecules ◦Strengthens against distortion Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Epithelial Tissue Epithelial Renewal and Repair ◦Exposure shortens cell life ◦Epithelium needs constant repair and replacement ◦Epithelial stem cells undergo mitosis ◦Epithelium grows up from base Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Epithelial Tissue Classifying Epithelia ◦Number of layers  Simple (one cell thick)  Stratified (multiple cells thick) ◦Cell shape  Squamous (flat)  Cuboidal (cubic)  Columnar (tall columns) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Epithelial Tissue Table 4-1

Epithelial Tissue Simple Squamous Epithelium Figure 4-4(a)

Epithelial Tissue Simple Cuboidal Epithelium Figure 4-4(b)

Epithelial Tissue Simple Columnar Epithelium Figure 4-4(c)

Epithelial Tissue Pseudostratified Ciliated Columnar Figure 4-5(a)

Epithelial Tissue Transitional Epithelium Figure 4-5(b)

Epithelial Tissue Stratified Squamous Epithelium Figure 4-5(c)

Epithelial Tissue Glandular Epithelia ◦Three secretion mechanisms  Merocrine ◦ Exocytosis of vesicles  Apocrine ◦ Release of apical cytoplasm  Holocrine ◦ Burst of entire contents Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Mechanisms of Glandular Secretion Figure 4-6

Glandular Epithelium Gland ◦Single cell or group of cells ◦Secrete substances into ducts, onto a surface, or into the blood

Glandular Epithelium Endocrine Glands ◦Secretions enter interstitial fluid and then diffuse directly into the bloodstream  Secretions = HORMONES ◦ Regulate metabolic and physiological activities to maintain homeostasis  Ex. Pituitary, thyroid, and adrenal glands

Glandular Epithelium Exocrine Glands ◦Secrete products into ducts that empty onto the surface of a covering and lining epithelium  Secretions include: ◦ Mucus ◦ Sweat ◦ Oil ◦ Earwax ◦ Saliva ◦ Digestive enzymes  Ex. Sudoriferous (sweat)glands ◦ Produce sweat to help lower body temperature  Ex. Salivary glands ◦ Secrete saliva  contains mucus and digestive enzymes

Glandular Epithelium Glands containing a combination of exocrine and endocrine tissue: ◦Pancreas ◦Ovaries ◦Testes

Classification of Exocrine Glands Unicellular glands ◦Single celled glands ◦Secrete mucus directly onto the surface of a lining epithelium Multicellular glands ◦Composed of many cells ◦Form distinctive microscopic structures or macroscopic organs  Ex: sudoriferous, sebaceous (oil), and salivary glands

Classification of Exocrine Glands Multicellular glands (continued) ◦Simple gland  Duct of the gland does not branch ◦Compound gland  Duct of the gland does branch ◦Tubular gland  Glands with tubular secretory parts ◦Acinar glands  Glands with rounded secretory portions ◦Tubuloacinar glands  Glands with both tubular and more rounded secretory portions

Classification of Exocrine Glands Simple Glands ◦Simple Tubular  Ex. Glands in the large intestine ◦Simple Branched Tubular  Ex. Gastric glands ◦Simple Coiled Tubular  Ex. Sweat glands

Classification of Exocrine Glands Simple Glands (continued) ◦Simple Acinar  Ex. Glands of the penile urethra ◦Simple Branched Acinar  Ex. Sebaceous glands

Classification of Exocrine Glands Compound Glands ◦Compound Tubular  Ex. Cowper’s glands ◦Compound Acinar  Ex. Mammary glands ◦Compound Tubuloacinar  Ex. Acinar glands of the pancreas

Intercellular Connections Cell Junctions ◦Contact points between plasma membranes of tissue cells ◦3 functions:  Forming seals between cells  Anchoring cells to one another or to extracellular material  Providing channels that allow ions and molecules to pass from cell to cell within a tissue

Intercellular Connections tight junctions ◦membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid Desmosomes ◦anchoring junctions ◦fasten cells together into strong sheets Gap junctions ◦communicating junctions ◦provide cytoplasmic channels between adjacent cells

LE 6-31 Tight junctions prevent fluid from moving across a layer of cells Tight junction 0.5 µm 1 µm 0.1 µm Gap junction Extracellular matrix Space between cells Plasma membranes of adjacent cells Intermediate filaments Tight junction Desmosome Gap junctions

Gap Junctions

Tight Junctions

Desmosomes

Connective Tissues Connective Tissues Components ◦Specialized cells ◦Extracellular matrix  Space between cells  Protein fibers  Fluid phase (the ground substance) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Connective Tissues Functions ◦Structural framework ◦Fluid and solute transport ◦Physical protection ◦Tissue interconnection ◦Fat storage ◦Microorganism defense Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Connective Tissues Classifying Connective Tissues ◦Connective tissue proper ◦Fluid connective tissues ◦Supporting connective tissues -blast = immature cells -cyte = mature cells Usually highly vascular ◦Except cartilage and tendons Have nerve supply ◦Except cartilage Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Connective Tissues Major Types of Connective Tissue Figure 4-7

Collagen Fibers ◦Strong, resist pulling forces ◦Promote flexibility and toughness ◦25% of total protein in body Elastic Fibers ◦Smaller than collagen fibers ◦Form a network within a tissue ◦Promote resilience ◦Consist of elastin and fibrillin ◦Found in skin, blood vessel walls, and lung tissue Reticular Fibers ◦Consist of collagen in bundles coated with glycoprotein ◦Support walls of blood vessels ◦Supporting framework for soft organs (spleen, lymph nodes)

Connective Tissues Connective Tissue Proper ◦Three types  Loose connective tissue ◦ Example: beneath dermis of skin  Adipose tissue ◦ Example: “love handles”  Dense connective tissue ◦ Examples: dermis, tendons, ligaments Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Connective Tissues Loose Connective Tissue Figure 4-9(a)

Connective Tissues Adipose Tissue Figure 4-9(b)

Connective Tissues Dense Connective Tissues Figure 4-9(c)

Connective Tissues Fluid Connective Tissues ◦Cells + a liquid ground substance  Blood ◦ RBCs, WBCs, platelets + plasma  Lymph ◦ Lymphocytes + lymph fluid Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Connective Tissues Supporting Connective Tissue ◦Support the body  Bone (osseous tissue) ◦ Osteocytes + collagen + calcium salts  Cartilage ◦ Chondrocytes + firm gel Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Connective Tissues Supporting Connective Tissue ◦Cartilage  Avascular  Covered by a fibrous perichondrium  Matrix primarily composed of collagen and proteoglycans  Cells called chondrocytes ◦ Found in lacunae (lacuna-singular) ◦ Maintain matrix  Three types of cartilage ◦ Hyaline cartilage ◦ Elastic cartilage ◦ Fibrocartilage Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Connective Tissues Hyaline Cartilage Figure 4-10(a)

Connective Tissues Elastic Cartilage Figure 4-10(b)

Connective Tissues Fibrocartilage Figure 4-10(c)

Connective Tissues Bone (Osseous Tissue) ◦Matrix provides unique properties  Collagen fibers resist bending  Calcium salts resist compression ◦Diffusion through canaliculi nourishes osteocytes ◦Covered by periosteum Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Connective Tissues Bone Figure 4-11

Membranes Types of Membranes ◦Mucous  Lines cavities that connect to exterior  Mucous moistens surface ◦ Examples: oral cavity, airways ◦Serous  Line internal cavities  Watery fluid moistens surface ◦ Example: peritoneal membrane Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Membranes Types of Membranes (continued) ◦Cutaneous  Covers body surface  Dry surface waterproofs the body ◦ Example: the skin ◦Synovial  Lines joints  Secretes slippery synovial fluid  Lubricates joints ◦ Examples: knee, elbow Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Membranes Membranes Figure 4-12

Muscle Tissue Properties of Muscle Tissue ◦Capable of contraction  Actin filaments  Myosin filaments ◦Three types of muscle tissue  Skeletal muscle  Cardiac muscle  Smooth muscle Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Muscle Tissue Skeletal Muscle Tissue Figure 4-13(a)

Muscle Tissue Cardiac Muscle Tissue Figure 4-13(b)

Muscle Tissue Smooth Muscle Tissue Figure 4-13(c)

Neural Tissue Figure 4-14

Tissue Injuries and Repair An injury harms multiple tissues simultaneously Tissues make coordinated response Responses restore homeostasis Two response types ◦Inflammation ◦Restoration Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Tissue Injuries and Repair Inflammation ◦Isolation of injured area ◦Cleanup of damaged tissue ◦Four signs of inflammation  Warmth  Redness  Swelling  Pain Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Tissue Injuries and Repair Regeneration ◦Repair/replacement of damaged tissue ◦Restoration of tissue function ◦Scar tissue from fibroblast activity ◦Complete, partial, or no regeneration ◦Tissue fibrosis common outcome  Formation of excess fibrous connective tissue Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Tissues and Aging Tissues Change with Age ◦Healing slows ◦Epithelia become thinner ◦Connective tissues become more fragile ◦Bones weaken, become brittle ◦Neuron and muscle fiber losses accumulate ◦Lifestyle interventions slow decline Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Tissues and Aging Aging and Cancer Incidence ◦25% develop cancer ◦Cancer risk rises with age ◦After heart disease, cancer second leading cause of death ◦Smoking linked to 40% of cancers ◦75% caused by environment Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings