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Tissues Cells work together in functionally related groups called tissues Tissue – a group of closely associated cells that perform related functions and are similar in structure
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Four Basic Tissue Types and Basic Functions
Epithelial tissue – covering Connective tissue – support Muscle tissue – movement Nervous tissue – control
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Covers a body surface or lines a body cavity Forms most glands
Epithelial Tissue Covers a body surface or lines a body cavity Forms most glands Functions of epithelium Protection Absorption, secretion, and ion transport Filtration Forms slippery surfaces
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Special Characteristics of Epithelia
Cellularity Specialized contacts Polarity Support by connective tissue Avascular but innervated Regeneration
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Special Characteristics of Epithelia
Figure 4.1
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Classifications of Epithelia
Figure 4.2
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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 wider than tall (plate-like) Cuboidal – cells are as wide as tall, like cubes Columnar – cells are taller than they are wide, like columns
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Simple Squamous Epithelium
Description – single layer of flat cells with disc-shaped nuclei Special types Endothelium (inner covering) – slick lining of hollow organs Mesothelium (middle covering) Lines peritoneal, pleural, and pericardial cavities Covers visceral organs of those cavities
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Simple Squamous Epithelium
Function Passage of materials by passive diffusion and filtration Secretes lubricating substances in serosae Location Renal corpuscles Alveoli of lungs Lining of heart, blood and lymphatic vessels Lining of ventral body cavity (serosae)
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Simple Squamous Epithelium
Figure 4.3a
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Simple Cuboidal Epithelium
Description – single layer of cube-like cells with large, spherical central nuclei Function – secretion and absorption Location – kidney tubules, secretory portions of small glands, ovary surface
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Simple Cuboidal Epithelium
Figure 4.3b
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Simple Columnar Epithelium
Description – single layer of column-shaped (rectangular) cells with oval nuclei Some bear cilia at their apical surface May contain goblet cells Function Absorption; secretion of mucus, enzymes, and other substances Ciliated type propels mucus or reproductive cells by ciliary action
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Simple Columnar Epithelium
Location Non-ciliated form Lines digestive tract, gallbladder, ducts of some glands Ciliated form Lines small bronchi, uterine tubes, and uterus
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Simple Columnar Epithelium
Figure 4.3c
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Pseudostratified Columnar Epithelium
Description All cells originate at basement membrane Only tall cells reach the apical surface May contain goblet cells and bear cilia Nuclei lie at varying heights within cells Gives false impression of stratification
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Pseudostratified Columnar Epithelium
Function – secretion of mucus; propulsion of mucus by cilia Locations Non-ciliated type Ducts of male reproductive tubes Ducts of large glands Ciliated variety Lines trachea and most of upper respiratory tract
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Pseudostratified Ciliated Columnar Epithelium
Figure 4.3d
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Stratified Epithelia Contain two or more layers of cells Regenerate from below Major role is protection Are named according to the shape of cells at apical layer
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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
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Stratified Squamous Epithelium
Specific types Keratinized – contain the protective protein keratin Surface cells are dead and full of keratin Non-keratinized – forms moist lining of body openings
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Stratified Squamous Epithelium
Function – Protects underlying tissues in areas subject to abrasion Location Keratinized – forms epidermis Non-keratinized – forms lining of esophagus, mouth, and vagina
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Stratified Squamous Epithelium
Figure 4.3e
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Stratified Cuboidal Epithelium
Description – generally two layers of cube-shaped cells Function – protection Location Forms largest ducts of sweat glands Forms ducts of mammary glands and salivary glands
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Stratified Cuboidal Epithelium
Figure 4.3f
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Stratified Columnar Epithelium
Description – several layers; basal cells usually cuboidal; superficial cells elongated Function – protection and secretion Location Rare tissue type Found in male urethra and large ducts of some glands
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Stratified Columnar Epithelium
Figure 4.3g
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Transitional Epithelium
Description Basal cells usually cuboidal or columnar Superficial cells dome-shaped or squamous Function – stretches and permits distension of urinary bladder Location Lines ureters, urinary bladder and part of urethra
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Transitional Epithelium
Figure 4.3h
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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
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Unicellular Exocrine Glands (The Goblet Cell)
Goblet cells produce mucin Mucin + water mucus Protects and lubricates many internal body surfaces (small intestine)
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Goblet Cells Figure 4.5
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Multicellular Exocrine Glands
Have two basic parts Epithelium-walled duct Secretory unit
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Multicellular Exocrine Glands
Classified by structure of duct Simple Compound Categorized by secretory unit Tubular Alveolar Tubuloalveolar
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Types of Multicellular Exocrine Glands
Figure 4.6
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Endocrine Glands Ductless glands Secrete substances directly into bloodstream Produce molecules called hormones
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Lateral Surface Features – Cell Junctions
Factors holding epithelial cells together Adhesion proteins link plasma membranes of adjacent cells Contours of adjacent cell membranes Special cell junctions
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Tight Junction Figure 4.7a
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Lateral Surface Features – Cell Junctions
Tight junctions (zona occludens) – close off intercellular space Found at apical region of most epithelial types Some proteins in plasma membrane of adjacent cells are fused Prevent molecules from passing between cells of epithelial tissue
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Desmosome Figure 4.7b
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Lateral Surface Features – Cell Junctions
Desmosomes – two disc-like plaques connected across intercellular space Plaques of adjoining cells are joined by proteins called cadherins Proteins interdigitate into extracellular space Intermediate filaments insert into plaques from cytoplasmic side
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Gap Junction Figure 4.7c
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Lateral Surface Features – Cell Junctions
Gap junctions – passageway between two adjacent cells Let small molecules move directly between neighboring cells Cells are connected by hollow cylinders of protein
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Basal Feature: The Basal Lamina
Non-cellular supporting sheet between the epithelium and the connective tissue deep to it Consists of proteins secreted by the epithelial cells Functions: Acts as a selective filter, determining which molecules from capillaries enter the epithelium Acts as scaffolding along which regenerating epithelial cells can migrate Basal lamina and reticular layers of the underlying connective tissue deep to it form the basement membrane
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Most diverse and abundant tissue Main classes
Connective Tissue Most diverse and abundant tissue Main classes Connective tissue proper Cartilage Bone tissue Blood Cells separated by large amount of extracellular matrix Common embryonic origin – mesenchyme
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Classes of Connective Tissue
Figure 4.9
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Major Functions of Connective Tissue
Support and binding of other tissues Holding body fluids Defending body against infection Storing nutrients as fat
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Connective Tissue Proper
Two main subclasses Loose connective tissue Dense connective tissue
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Areolar Connective Tissue – A Model Connective Tissue
Underlies epithelial tissue Surrounds small nerves and blood vessels Has structures and functions shared by other connective tissues Borders all other tissues in the body Fibers provide support Three types of protein fibers in extracellular matrix Collagen fibers Reticular fibers Elastic fibers Fibroblasts produce these fibers
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Areolar Connective Tissue
Description Gel-like matrix with all three fiber types Cells – fibroblasts, macrophages, mast cells, white blood cells Function Wraps and cushions organs Holds and conveys tissue fluid Important role in inflammation
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Areolar Connective Tissue
Location Widely distributed under epithelia Packages organs Surrounds capillaries
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Areolar Connective Tissue
Figure 4.12b
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Adipose Tissue Description Closely packed adipocytes
Have nucleus pushed to one side by fat droplet
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Adipose Tissue Function Location Provides reserve food fuel
Insulates against heat loss Supports and protects organs Location Under skin Around kidneys Behind eyeballs, within abdomen and in breasts
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Adipose Tissue Figure 4.12c
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Reticular Connective Tissue
Description – network of reticular fibers in loose ground substance Function – form a soft, internal skeleton (stroma) – supports other cell types Location – lymphoid organs Lymph nodes, bone marrow, and spleen
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Reticular Connective Tissue
Figure 4.12d
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Dense Connective Tissue
Dense irregular connective tissue Dense regular connective tissue
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Dense Irregular Connective Tissue
Description Primarily irregularly arranged collagen fibers Some elastic fibers and fibroblasts
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Dense Irregular Connective Tissue
Function Withstands tension Provides structural strength Location Dermis of skin Submucosa of digestive tract Fibrous capsules of joints and organs
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Dense Irregular Connective Tissue
Figure 4.12e
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Dense Regular Connective Tissue
Description Primarily parallel collagen fibers Fibroblasts and some elastic fibers Poorly vascularized
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Dense Regular Connective Tissue
Function Attaches muscle to bone Attaches bone to bone Withstands great stress in one direction Location Tendons and ligaments Aponeuroses Fascia around muscles
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Dense Regular Connective Tissue
Figure 4.12f
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Other Connective Tissues
Cartilage Bone Blood
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Cartilage Firm, flexible tissue Contains no blood vessels or nerves Matrix contains up to 80% water Cell type – chondrocyte
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Types of Cartilage Hyaline cartilage Elastic cartilage Fibrocartilage
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Hyaline Cartilage Description
Imperceptible collagen fibers (hyaline = glassy) Chodroblasts produce matrix Chondrocytes lie in lacunae
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Hyaline Cartilage Function Supports and reinforces Resilient cushion
Resists repetitive stress
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Hyaline Cartilage Location Fetal skeleton Ends of long bones
Costal cartilage of ribs Cartilages of nose, trachea, and larynx
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Hyaline Cartilage Figure 4.12g
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Elastic Cartilage Description Similar to hyaline cartilage
More elastic fibers in matrix
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Elastic Cartilage Function Location Maintains shape of structure
Allows great flexibility Location Supports external ear Epiglottis
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Elastic Cartilage Figure 4.12h
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Fibrocartilage Description Function
Matrix similar, but less firm than hyaline cartilage Thick collagen fibers predominate Function Tensile strength and ability to absorb compressive shock
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Fibrocartilage Location Intervertebral discs Pubic symphysis
Discs of knee joint
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Fibrocartilage Figure 4.12i
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Bone Tissue Description
Calcified matrix containing many collagen fibers Osteoblasts – secrete collagen fibers and matrix Osteocytes – mature bone cells in lacunae Very well vascularized
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Bone Tissue Function Location Supports and protects organs
Provides levers and attachment site for muscles Stores calcium and other minerals Stores fat Marrow is site for blood cell formation Location Bones
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Bone Tissue Figure 4.12j
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Blood Tissue An atypical connective tissue Develops from mesenchyme Consists of cells surrounded by nonliving matrix
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Blood Tissue Description – red and white blood cells in a fluid matrix Function – transport of respiratory gases, nutrients, and wastes Location – within blood vessels
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Blood Tissue Figure 4.12k
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Covering and Lining Membranes
Combine epithelial tissues and connective tissues Cover broad areas within body Consist of epithelial sheet plus underlying connective tissue
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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
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Three Types of Membranes
Serous membrane – slippery membranes Simple squamous epithelium lying on areolar connective tissue Line closed cavities Pleural, peritoneal, and pericardial cavities
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Covering and Lining Membranes
Figure 4.13a, b
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Covering and Lining Membranes
Figure 4.13c
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Muscle Tissue Skeletal muscle tissue Cardiac muscle tissue Smooth muscle tissue
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Skeletal Muscle Tissue
Description Long, cylindrical cells Multinucleate Obvious striations
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Skeletal Muscle Tissue
Function Voluntary movement Manipulation of environment Facial expression Location Skeletal muscles attached to bones (occasionally to skin)
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Skeletal Muscle Tissue
Figure 4.14a
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Cardiac Muscle Tissue Description Branching cells, striated
Generally uninucleate Cells interdigitate at intercalated discs
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Cardiac Muscle Tissue Function Location
Contracts to propel blood into circulatory system Location Occurs in walls of heart
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Cardiac Muscle Tissue Figure 4.14b
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Smooth Muscle Tissue Description
Spindle-shaped cells with central nuclei Arranged closely to form sheets No striations
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Smooth Muscle Tissue Function Location
Propels substances along internal passageways Involuntary control Location Mostly walls of hollow organs
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Smooth Muscle Tissue Figure 4.14c
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Nervous Tissue Description
Main components are brain, spinal cord, and nerves Contains two types of cells Neurons – excitatory cells Supporting cells (neuroglial cells)
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Nervous Tissue Function Location
Transmit electrical signals from sensory receptors to effectors Location Brain, spinal cord, and nerves
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Nervous Tissue Figure 4.15
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Tissue Response to Injury
Inflammatory response – non-specific, local response Limits damage to injury site Immune response – takes longer to develop and very specific Destroys particular microorganisms at site of infection
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Acute inflammation – heat, redness, swelling, and pain
Chemicals signal nearby blood vessels to dilate Histamine increases permeability of capillaries
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Edema – accumulation of fluid
Inflammation Edema – accumulation of fluid Helps dilute toxins secreted by bacteria Brings oxygen and nutrients from blood Brings antibodies from blood to fight infection
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Repair Regeneration – replacement of destroyed tissue with same type of tissue Fibrosis – proliferation of scar tissue Organization – clot is replaced by granulation tissue
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Tissue Repair of a Skin Wound
Figure 4.16a
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Tissue Repair of a Skin Wound
Figure 4.16b
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Tissue Repair of a Skin Wound
Figure 4.16c
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The Tissues Throughout Life
At the end of second month of development: Primary tissue types have appeared Major organs are in place Adulthood Only a few tissues regenerate Many tissues still retain populations of stem cells
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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
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