TISSUES  Tissues are communities of cells working together to perform a function for the organism.  Remember at all times that we are still talking about CELLS!  Even though commonly we think of organs as heart, lungs, kidney etc. that other tissues are also called organs such as muscles, bones etc.

Four Basic Tissue Types and Basic Functions  Epithelial tissue – covering - ectoderm  Connective tissue – support – mesoderm/endoderm  Muscle tissue – movement - mesoderm  Nervous tissue – control - ectoderm

Epithelial Tissue  Covers the body surface and lines body cavities  Forms parts of most glands (organs are mainly epithial and connective tissues with nerves and blood vessels serving the cells)  Functions of epithelium  Protection – part of immune system  Absorption (intestine), secretion (glands), and ion transport (nephron tubules)  Filtration (capillaries)  Forms slippery surfaces (mucus membranes)  Glandular Epithelium (sweat, oil, wax, hormones, mucus)  Greatest capacity for regeneration (therefore is the origin of most cancers)

Classifications of Epithelia  First name of tissue indicates number of cell layers  Simple – one layer of cells  Stratified – more than one layer of cells  Last name of tissue describes shape of cells  Squamous – cells are wider than tall (plate- like)  Cuboidal – cells are as wide as tall, like cubes  Columnar – cells are taller than they are wide, like columns

EPITHELIUM AS GLANDS  EXOCRINE GLANDS –with ducts  ENDOCRINE GLANDS – without ducts

Exocrine Glands  Ducts carry products of exocrine glands to epithelial surface  Include the following diverse glands  Mucus-secreting glands  Sweat and oil glands  Salivary glands  Liver and pancreas  Goblet cells produce mucin  Mucin + water  mucus  Protects and lubricates many internal body surfaces  Goblet cells are a unicellular exocrine gland and are epithelial

Goblet Cells – a type of epithelial cell (Unicellular gland) Figure 4.5

Multicellular Exocrine Glands  Have two basic parts  Epithelium-walled duct  Secretory unit  Classified by structure of duct  Simple  Compound  Categorized by secretory unit  Tubular  Alveolar  Tubuloalveolar

Types of Multicellular Exocrine Glands Figure 4.6 For information only!

Endocrine Glands  Endocrine glands are ductless glands  Secrete substances directly into extracellular space to be picked up by the bloodstream by diffusion  Produce molecules called hormones

Special Characteristics of Epithelia 1) Cellularity - c ells separated by minimal extra cellular material 2) Specialized contacts - c ells joined by specialized cell junctions 3) Polarity - c ell regions of the apical surface differ from the basal surface

Special Contacts (Lateral Surface Features) – Cell Junctions  Think about the function of epithelial tissues and what characteristics it would have to have to perform that function.  Since exposure to digested food would be very dangerous if exposed to the contents of the abdominal cavity, the intestinal tissue needs to be a barrier.  Therefore, cells need to be tightly held together  Factors holding epithelial cells together  Adhesion proteins link plasma membranes of adjacent cells  Contours of adjacent cell membranes  (Like puzzle pieces)  Special cell junctions

A) Tight Junction Figure 4.7a Tight junctions (zona occludens) – close off intercellular space

B) Desmosome Figure 4.7b Desmosomes – two disclike plaques connected across intercellular space

C) Gap Junction Figure 4.7c Gap junctions – passageway between two adjacent cells

D) Adherens Junctions Has linker proteins; Important for the skin Zonula adherens

Special Characteristics of Epithelia 4) Support by connective tissue 5) Avascular but innervated - Epithelia receive nutrients from underlying connective tissue 6) Regeneration - Lost cells are quickly replaced by cell division

Basal Feature: The Basal Lamina  Noncellular supporting sheet between the ET and the CT deep to it  Consists of proteins secreted by ET cells

Basal Lamina  Damage to the basal lamina due to untreated diabetes may lead to kidney failure and blindness.

Basal Feature: The Basal Lamina  Functions  Acts as a selective filter, determining which molecules from capillaries enter the epithelium  Acts as scaffolding along which regenerating ET cells can migrate  Basal lamina and reticular layers of the underlying CT deep to it form the basement membrane

Epithelial Apical Surface Features  Apical surface features 1) Microvilli – fingerlike extensions of plasma membrane  Abundant in ET of small intestine and kidney  Maximize surface area across which small molecules enter or leave  Act as stiff knobs that resist abrasion 2) Cilia – whiplike, highly motile extensions of apical surface membranes  Contains a core of nine pairs of microtubules encircling one middle pair  Each pair of microtubules – arranged in a doublet  Movement of cilia – in coordinated waves

Cilia – found in upper respiratory passageways Figure 4.8 For information only

Simple Squamous Epithelium  Description – single layer – flat cells with disc- shaped nuclei  Specialized types  Endothelium (inner covering) – slick lining of hollow organs  Mesothelium (middle covering)  Lines peritoneal, pleural, pericardial cavities  Covers visceral organs of those cavities

Simple Squamous Epithelium Figure 4.3a

Simple Cuboidal Epithelium Figure 4.3b

Simple Columnar Epithelium Figure 4.3c

Pseudostratified Ciliated Columnar Epithelium Figure 4.3d

Stratified Epithelia  Properties  Contain two or more layers of cells  Regenerate from below (basal layer)  Major role is protection  Named according to shape of cells at apical layer

Stratified Squamous Epithelium  Description  Many layers of cells – squamous in shape  Deeper layers of cells appear cuboidal or columnar  Thickest epithelial tissue  Adapted for protection from abrasion

Stratified Squamous Epithelium  Two types  Keratinized and nonkeratinized  Keratinized  Location – epidermis  Contains the protective protein keratin  Waterproof  Surface cells are dead and full of keratin  Nonkeratinized  Forms moist lining of body openings

Stratified Squamous Epithelium Figure 4.3e

Stratified Cuboidal Epithelium Figure 4.3f

Stratified Columnar Epithelium Figure 4.3g

Transitional Epithelium Figure 4.3h

Classes of Connective Tissue  Most diverse and abundant tissue  Main classes  Connective tissue proper  Cartilage  Bone tissue  Blood and fat!  Cells separated by large amount of extracellular matrix  Common embryonic origin – mesenchyme  Extracellular matrix is composed of ground substance

Classes of Connective Tissue Figure 4.9

Connective Tissue Proper  Has two subclasses  Loose connective tissue  Areolar, adipose, and reticular  Dense connective tissue  Dense irregular, dense regular, and elastic This cell type is the most divers and abundant type of tissue

Areolar Connective Tissue – A Model Connective Tissue  Areolar connective tissue  Underlies epithelial tissue  Surrounds small nerves and blood vessels  Has structures and functions shared by other CT  Borders all other tissues in the body  Is a “model” connective tissue – why?  It has all 3 fiber types: Reticular, elastic and collagen fibers

Major Functions of Connective Tissue  Structures within areolar CT and function  Support and binding of other tissues  Holding body fluids (interstitial fluid  lymph)  Defending body against infection  Storing nutrients as fat

Areolar Connective Tissue  Fibers provide support  Three types of protein fibers in extracellular matrix  Collagen fibers  Reticular fibers  Elastic fibers  Fibroblasts produce these fibers

Areolar Connective Tissue Figure 4.12b

Areolar Connective Tissue  Tissue fluid (interstitial fluid)  Watery fluid occupying extracellular matrix  Tissue fluid derives from blood  Ground substance  Viscous, spongy part of extracellular matrix  Consists of sugar and protein molecules  Made and secreted by fibroblasts

Areolar Connective Tissue  Main battlefield in fight against infection  Defenders gather at infection sites  Macrophages  Plasma cells  Mast cells  White blood cells  Neutrophils, lymphocytes, and eosinophils

Adipose Tissue Figure 4.12c

Reticular Connective Tissue Figure 4.12d

Dense Connective Tissue  Dense irregular connective tissue  Dense regular connective tissue  Elastic connective tissue

Dense Irregular Connective Tissue Figure 4.12e

Dense Regular Connective Tissue Figure 4.12f

Elastic Connective Tissue Figure 4.12g

Other Connective Tissues  Cartilage  Bone  Blood

Cartilage  Firm, flexible tissue  Contains no blood vessels or nerves  Matrix contains up to 80% water  Cell type – chondrocyte

Types of Cartilage  Hyaline cartilage  Elastic cartilage  Fibrocartilage

Hyaline Cartilage Figure 4.12h  collagen fibers (hyaline = glassy); Chodroblasts produce matrix; Chondrocytes lie in lacunae

Elastic Cartilage Figure 4.12i

Fibrocartilage Figure 4.12j

Bone Tissue  Description  Calcified matrix containing many collagen fibers  Osteoblasts – secrete collagen fibers and matrix  Osteocytes – mature bone cells in lacunae  Well vascularized

Bone Tissue Figure 4.12k

Blood Tissue  An atypical connective tissue  Develops from mesenchyme  Consists of cells surrounded by nonliving matrix

Blood Tissue Figure 4.12l

Muscle Tissue  Skeletal muscle tissue  Cardiac muscle tissue  Smooth muscle tissue

Skeletal Muscle Tissue Figure 4.14a

Cardiac Muscle Tissue Figure 4.14b

Smooth Muscle Tissue Figure 4.14c

Nervous Tissue  Description  Main components are brain, spinal cord, and nerves  Contains two types of cells  Neurons – excitatory cells  Supporting cells (neuroglial cells)

Nervous Tissue Figure 4.15

The Tissues Throughout Life  With increasing age  Epithelia thin  Collagen decreases  Bones, muscles, and nervous tissue begin to atrophy  Poor nutrition and poor circulation – poor health of tissues

Covering and Lining Membranes  Combine epithelial tissues and connective tissues  Cover broad areas within body  Consist of epithelial sheet plus underlying connective tissue

Three Types of Membranes  Cutaneous membrane – skin  Mucous membrane  Lines hollow organs that open to surface of body  An epithelial sheet underlain with layer of lamina propria

Three Types of Membranes  Serous membrane – slippery membranes  Simple squamous epithelium lying on areolar connective tissue  Line closed cavities  Pleural, peritoneal, and pericardial cavities

Covering and Lining Membranes Figure 4.13a, b

Covering and Lining Membranes Figure 4.13c

HOMEWORK  What are the four tissue types, where are they found in the body and what are their general functions?  Name the 3 shapes of epithelial tissue and their subtypes and where they would be found on the body  What are the features of the basal surface, the apical surface and the lateral surfaces of epithelial tissues?  What are the various cell junctions and in which tissues (specifically, where in the body) would they be found?  What is a gland? How many types of glands are there and what do they secrete?  What type of tissue is bone, tendon, ligaments, blood, fat, nerves, muscles?  What is the simple squamous layer that lines blood vessels called?

HOMEWORK  What are the types of connective tissues, where would they be found in the body and what are their functions?  What are the filaments (fibers) which are secreted by CT?  What are the contents of loose areolar tissue?  What is the difference between DICT and DRCT?  What type of tissue is a tendon made of?  What are the three types of muscle tissue?  How do you distinguish cardiac from skeletal muscle?  How do you distinguish smooth muscle from skeletal muscle?  What is the last tissue type? What is it’s function?  Elastic fibers are composed of?  IVD are made of? (intervertebral discs)

 Name all cell junction types and what are their distinguishing features?  How many layers is pseudostratified epithelium?