Anatomy & PhysiologyAnatomy & Physiology

Lesson 4Lesson 4

HISTOLOGYHISTOLOGY

HistologyHistology is the study of the structure of is the study of the structure of tissues.tissues.

A A tissuetissue is a group of similar cells and is a group of similar cells and their intercellular substance, function their intercellular substance, function together to perform a specialized activity.together to perform a specialized activity.

Tissues in the body can be classified into Tissues in the body can be classified into four principle types, according to their four principle types, according to their structure and function.structure and function.

TYPES OF TISSUESTYPES OF TISSUES Epithelial tissueEpithelial tissue—covers body surfaces, lines —covers body surfaces, lines

hollow organs, body cavities, and ducts, and hollow organs, body cavities, and ducts, and forms glands.forms glands.

Connective tissueConnective tissue—protects and supports the —protects and supports the body and its organs, binds organs together, body and its organs, binds organs together, stores energy reserves as fat, and provides stores energy reserves as fat, and provides immunity.immunity.

Muscle tissueMuscle tissue—responsible for movement and —responsible for movement and generation of force.generation of force.

Nervous tissueNervous tissue—initiates and transmits action —initiates and transmits action potentials (nerve impulses) that help coordinate potentials (nerve impulses) that help coordinate body activities.body activities.

EPITHELIAL TISSUEEPITHELIAL TISSUE

Epithelial tissue (or epithelium) can be Epithelial tissue (or epithelium) can be divided into two types:divided into two types: Covering and lining epitheliumCovering and lining epithelium—forms skin, —forms skin,

outer covering of some organs, lines body outer covering of some organs, lines body cavities and the inside of the respiratory and cavities and the inside of the respiratory and digestive tracts, blood vessels, and ducts.digestive tracts, blood vessels, and ducts.

Glandular epitheliumGlandular epithelium—forms the secreting —forms the secreting portion of glands.portion of glands.

GENERAL FEATURES OF GENERAL FEATURES OF EPITHELIAL TISSUESEPITHELIAL TISSUES

Consist of mostly or entirely tightly packed cells with little Consist of mostly or entirely tightly packed cells with little or no extracellular material between cells.or no extracellular material between cells.

Cells are arranged in continuous sheets, in either single Cells are arranged in continuous sheets, in either single or multiple layers.or multiple layers.

Cell layers have an Cell layers have an apical (free) surfaceapical (free) surface, which is , which is exposed to a body cavity, lining of an internal organ, or exposed to a body cavity, lining of an internal organ, or the exterior of the body, and a the exterior of the body, and a basal surfacebasal surface, which is , which is attaced to the basement membrane.attaced to the basement membrane.

Cells have many junctions, providing secure attachments Cells have many junctions, providing secure attachments between cells.between cells.

Tissues are Tissues are avascularavascular—blood vessels that supply —blood vessels that supply nutrients and remove wastes are located in the adjacent nutrients and remove wastes are located in the adjacent connective tissue. Materials move between epithelium connective tissue. Materials move between epithelium and connective tissue by diffusion.and connective tissue by diffusion.

Have a nerve supply. Have a nerve supply. Diverse in origin—are derived from all three primary Diverse in origin—are derived from all three primary

germ layers.germ layers.

GENERAL FEATURES OF GENERAL FEATURES OF EPITHELIAL TISSUESEPITHELIAL TISSUES

Adhere firmly to adjacent connective tissue, which holds Adhere firmly to adjacent connective tissue, which holds the epithelium in place and prevents it from tearing. the epithelium in place and prevents it from tearing. Connection between the epithelium and the connective Connection between the epithelium and the connective tissue is via a thin tissue is via a thin basement membranebasement membrane, which is , which is composed of the composed of the basal laminabasal lamina (collagen, laminin, and (collagen, laminin, and proteoglycans) and the proteoglycans) and the reticular lamina reticular lamina (reticular fibers, (reticular fibers, fibroconectin, and glycoproteins). The basement fibroconectin, and glycoproteins). The basement membrane provides cell attachment and physical membrane provides cell attachment and physical support for the epithelium, acts a filter in the kidneys, support for the epithelium, acts a filter in the kidneys, and guides cell migration during development and tissue and guides cell migration during development and tissue repair.repair.

Have a high capacity for renewal (high mitotic rate) Have a high capacity for renewal (high mitotic rate) because they are subject to wear and tear and injury.because they are subject to wear and tear and injury.

Functions include: protection, filtration, lubrication, Functions include: protection, filtration, lubrication, secretion, digestion, absorption, transportation, secretion, digestion, absorption, transportation, excretion, sensory reception, and reproduction.excretion, sensory reception, and reproduction.

EPITHELIAL TISSUEEPITHELIAL TISSUE

TYPES OF EPITHELIAL TISSUETYPES OF EPITHELIAL TISSUE Simple squamous epitheliumSimple squamous epithelium

Description: Single layer of flat cells.Description: Single layer of flat cells. Location: Lines heart, blood vessels, lymphatic Location: Lines heart, blood vessels, lymphatic

vessels, air sacs of lungs, glomerular capsule of vessels, air sacs of lungs, glomerular capsule of kidneys, and inner surface of the eardrum. Forms kidneys, and inner surface of the eardrum. Forms epithelial layer of serous membranes.epithelial layer of serous membranes.

Function: Filtration, diffusion, osmosis, and secretion Function: Filtration, diffusion, osmosis, and secretion in serous membranes.in serous membranes.

TYPES OF EPITHELIAL TISSUETYPES OF EPITHELIAL TISSUE Simple cuboidal epithelium:Simple cuboidal epithelium:

Description: Single layer of cube-shaped cells.Description: Single layer of cube-shaped cells. Location: Covers surface of ovary, lines anterior Location: Covers surface of ovary, lines anterior

surface of eye lens capsule, forms pigmented surface of eye lens capsule, forms pigmented epithelium at back of eye, lines kidney tubules and epithelium at back of eye, lines kidney tubules and smaller ducts of many glands.smaller ducts of many glands.

Function: Secretion and absorption.Function: Secretion and absorption.

TYPES OF EPITHELIAL TISSUETYPES OF EPITHELIAL TISSUE Nonciliated simple columnar epithelium:Nonciliated simple columnar epithelium:

Description: Single layer of nonciliated rectangular Description: Single layer of nonciliated rectangular cells. Contains cells. Contains goblet cellsgoblet cells (secrete mucus) and (secrete mucus) and microvillimicrovilli (fingerlike projections that increase the (fingerlike projections that increase the plasma membrane surface area) in some locations.plasma membrane surface area) in some locations.

Location: Lines GI tract from the stomach to the anus, Location: Lines GI tract from the stomach to the anus, ducts of many glands, and gallbladder.ducts of many glands, and gallbladder.

Function: Secretion and absorption.Function: Secretion and absorption.

TYPES OF EPITHELIAL TISSUETYPES OF EPITHELIAL TISSUE Ciliated simple columnar Ciliated simple columnar

epithelium:epithelium: Description: Single layer of ciliated Description: Single layer of ciliated

rectangular cells. Contains goblet rectangular cells. Contains goblet cells in some locations.cells in some locations.

Location: Lines a few portions of Location: Lines a few portions of upper respiratory tract, Fallopian upper respiratory tract, Fallopian tubes, uterus, some paranasal tubes, uterus, some paranasal sinuses, and central canal of sinuses, and central canal of spinal cord.spinal cord.

Function: Moves fluids or particles Function: Moves fluids or particles along a passageway by ciliary along a passageway by ciliary action.action.

TYPES OF EPITHELIAL TISSUETYPES OF EPITHELIAL TISSUE Stratified squamous Stratified squamous

epithelium:epithelium: Description: Multiple cell layers. Description: Multiple cell layers.

Deep layers are cuboidal to Deep layers are cuboidal to columnar in shape. Superficial columnar in shape. Superficial layers consist of squamous cells. layers consist of squamous cells. As surface cells are lost, they are As surface cells are lost, they are replaced by basal cells.replaced by basal cells.

Location: Keratinizing variety Location: Keratinizing variety forms superficial layer of skin. forms superficial layer of skin. Nonkeratinizing variety lines wet Nonkeratinizing variety lines wet surfaces, such as lining of the surfaces, such as lining of the mouth, esophagus, part of mouth, esophagus, part of epiglottis, vagina, and covers epiglottis, vagina, and covers tongue.tongue.

Function: Protection.Function: Protection.

TYPES OF EPITHELIAL TISSUETYPES OF EPITHELIAL TISSUE Stratified cuboidal epithelium:Stratified cuboidal epithelium:

Description: Two or more layers of cells in Description: Two or more layers of cells in which the superficial cells are cube-shaped.which the superficial cells are cube-shaped.

Location: Ducts of adult sweat glands and Location: Ducts of adult sweat glands and part of male urethra.part of male urethra.

Function: Protection.Function: Protection.

TYPES OF EPITHELIAL TISSUETYPES OF EPITHELIAL TISSUE Stratified columnar Stratified columnar

epithelium:epithelium: Description: Several layers of Description: Several layers of

polyhedral cells. Columnar polyhedral cells. Columnar cells are only in the superficial cells are only in the superficial layer.layer.

Location: Lines part of urethra, Location: Lines part of urethra, large excretory ducts of some large excretory ducts of some glands, small areas in anal glands, small areas in anal mucus membrane, and part of mucus membrane, and part of the conjuctiva of the eye.the conjuctiva of the eye.

Function: Protection and Function: Protection and secretion.secretion.

TYPES OF EPITHELIAL TISSUETYPES OF EPITHELIAL TISSUE Transitional epitheliumTransitional epithelium

Description: Appearance is Description: Appearance is variable. Shape of variable. Shape of superficial cells ranges from superficial cells ranges from squamous to cuboidal, squamous to cuboidal, depending on the degree of depending on the degree of distention (stretching).distention (stretching).

Location: Lines urinary Location: Lines urinary bladder and portions of bladder and portions of ureters and urethra.ureters and urethra.

Function: Permits Function: Permits distention.distention.

TYPES OF EPITHELIAL TISSUETYPES OF EPITHELIAL TISSUE Pseudostratified columnar epithelium:Pseudostratified columnar epithelium:

Description: Not a true stratified tissue. Nuclei of cells Description: Not a true stratified tissue. Nuclei of cells are at different levels. All cells are attached to the are at different levels. All cells are attached to the basement membrane, but not all reach the free basement membrane, but not all reach the free surface.surface.

Location: Ciliated lines most of upper respiratory tract. Location: Ciliated lines most of upper respiratory tract. Nonciliated lines larger ducts of many glands, Nonciliated lines larger ducts of many glands, epididymis, and part of male urethra.epididymis, and part of male urethra.

Funtion: Secretion and movement of mucus by ciliary Funtion: Secretion and movement of mucus by ciliary action.action.

TYPES OF EPITHELIAL TISSUE TYPES OF EPITHELIAL TISSUE (GLANDULAR)(GLANDULAR)

Exocrine glands:Exocrine glands: Description: Secretory products released into Description: Secretory products released into ductsducts.. Location: Sweat, oil, ear wax, and mammary glands Location: Sweat, oil, ear wax, and mammary glands

of the skin, digestive glands (like salivary glands and of the skin, digestive glands (like salivary glands and pancreas).pancreas).

Function: Produce mucus, perspiration, oil, ear wax, Function: Produce mucus, perspiration, oil, ear wax, milk, or digestive enzymes.milk, or digestive enzymes.

Endocrine glands:Endocrine glands: Description: Secretory products (hormones) diffuse Description: Secretory products (hormones) diffuse

into blood after passing through extracellular fluid.into blood after passing through extracellular fluid. Location: Pituitary gland, pineal gland, thyroid and Location: Pituitary gland, pineal gland, thyroid and

parathyroid glands, adrenal glands, pancreas, parathyroid glands, adrenal glands, pancreas, ovaries, testes, thymus gland, etc.ovaries, testes, thymus gland, etc.

Function: Produce hormones that regulate various Function: Produce hormones that regulate various body activities.body activities.

CONNECTIVE TISSUECONNECTIVE TISSUE Connective tissue is the most abundant, widely Connective tissue is the most abundant, widely

distributed (and diverse) tissue in the body. It can be distributed (and diverse) tissue in the body. It can be divided into two classifications, with several subclasses:divided into two classifications, with several subclasses:

Embryonic connective tissueEmbryonic connective tissue• MesenchymeMesenchyme• Mucous connective tissueMucous connective tissue

Mature connective tissueMature connective tissue• Loose connective tissueLoose connective tissue

Areolar connective tissueAreolar connective tissue Adipose connective tissueAdipose connective tissue Reticular connective tissueReticular connective tissue

• Dense connective tissueDense connective tissue Dense regular connective tissueDense regular connective tissue Dense irregular connective tissueDense irregular connective tissue Elastic connective tissueElastic connective tissue

• CartilageCartilage Hyaline cartilageHyaline cartilage FibrocartilageFibrocartilage Elastic cartilageElastic cartilage

• Bone (osseous) tissueBone (osseous) tissue• Blood (vascular tissue)Blood (vascular tissue)

GENERAL FEATURES OF GENERAL FEATURES OF CONNECTIVE TISSUECONNECTIVE TISSUE

Consists of three basic elements: Cells, ground Consists of three basic elements: Cells, ground substance, and fibers. Together, the ground substance substance, and fibers. Together, the ground substance and fibers form the extracellular and fibers form the extracellular matrixmatrix. Connective . Connective tissue cells are surrounded by large amounts of matrix, tissue cells are surrounded by large amounts of matrix, so they seldom touch eachother.so they seldom touch eachother.

Connective tissues usually do not occur on free Connective tissues usually do not occur on free surfaces. However, joint cavities are lined by areolar surfaces. However, joint cavities are lined by areolar connective tissue.connective tissue.

Except for cartilage, connective tissue has a nerve Except for cartilage, connective tissue has a nerve supply.supply.

Usually is highly vascular (has a rich blood supply). Usually is highly vascular (has a rich blood supply). Exceptions are cartilage (no blood supply) and tendons Exceptions are cartilage (no blood supply) and tendons (scant blood supply).(scant blood supply).

The matrix, which may be fluid, semifluid, gelatinous, The matrix, which may be fluid, semifluid, gelatinous, fibrous, or calcified, is usually secreted by the connective fibrous, or calcified, is usually secreted by the connective tissue cells and adjacent cells and determines the tissue cells and adjacent cells and determines the tissue’s physical qualities.tissue’s physical qualities.

CONNECTIVE TISSUE CELLSCONNECTIVE TISSUE CELLS

Derived from embryonic mesodermal cells Derived from embryonic mesodermal cells (mesenchymal cells).(mesenchymal cells).

The immature cells have names that end in The immature cells have names that end in ––blastblast (fibroblasts, chondroblasts, osteoblasts). (fibroblasts, chondroblasts, osteoblasts). These cells retain the ability to undergo mitosis These cells retain the ability to undergo mitosis and produce matrix.and produce matrix.

The mature cells have names that end in The mature cells have names that end in –cyte–cyte (chondrocyte, osteocyte). Mature cells have (chondrocyte, osteocyte). Mature cells have decreased capacity for cell division and matrix decreased capacity for cell division and matrix formation. They are mostly responsible for formation. They are mostly responsible for maintaining the matrix.maintaining the matrix.

CONNECTIVE TISSUE CELLSCONNECTIVE TISSUE CELLS Some connective tissue cells include:Some connective tissue cells include:

FibroblastsFibroblasts—Large, flat, spindle-shaped cells with branching —Large, flat, spindle-shaped cells with branching processes. Secrete the molecules that form the matrix.processes. Secrete the molecules that form the matrix.

Macrophages (histiocytes)Macrophages (histiocytes)—Develop from —Develop from monocytesmonocytes (a type (a type of white blood cell). Irregular shape with short, branching of white blood cell). Irregular shape with short, branching projections that engulf bacteria and cellular debris by projections that engulf bacteria and cellular debris by phagocytosis, providing defense for the body. Wandering phagocytosis, providing defense for the body. Wandering macrophages leave the blood and travel to infected tissues while macrophages leave the blood and travel to infected tissues while fixed macrophages remain in certain tissues and organs.fixed macrophages remain in certain tissues and organs.

Plasma cellsPlasma cells—Small and either round or irregularly shaped. —Small and either round or irregularly shaped. Develop from Develop from B lymphocytesB lymphocytes (a type of white blood cell). (a type of white blood cell). Secrete antibodies and provide immunity. Found throughout the Secrete antibodies and provide immunity. Found throughout the body, but mostly in connective tissues—especially in the GI tract body, but mostly in connective tissues—especially in the GI tract and mammary glands.and mammary glands.

Mast cellsMast cells—Abundant alongside blood vessels. Produce —Abundant alongside blood vessels. Produce histamine, which dilates small blood vessels during histamine, which dilates small blood vessels during inflammation.inflammation.

CONNECTIVE TISSUE MATRIXCONNECTIVE TISSUE MATRIX Ground Substance:Ground Substance:

Supports cells, binds them together, provides a medium for Supports cells, binds them together, provides a medium for transport of substances between blood and cells, influences transport of substances between blood and cells, influences tissue development, migration, proliferation, shape, and tissue development, migration, proliferation, shape, and metabolic functions of tissues.metabolic functions of tissues.

Contains a variety of large, complex molecules, including:Contains a variety of large, complex molecules, including:• Hyaluronic acidHyaluronic acid—viscous, slippery substance that binds cells —viscous, slippery substance that binds cells

together, lubricates joints, and help maintain shape of eyeball.together, lubricates joints, and help maintain shape of eyeball.• Chondroitin sulfateChondroitin sulfate—jellylike substance that provides support and —jellylike substance that provides support and

adhesiveness in cartilage, bone, skin, and blood vessels.adhesiveness in cartilage, bone, skin, and blood vessels.• Dermatan sulfateDermatan sulfate—exists in skin, tendons, blood vessels, and —exists in skin, tendons, blood vessels, and

heart valves.heart valves.• Keratan sulfateKeratan sulfate—exists in bone, cartilage, and the cornea of the —exists in bone, cartilage, and the cornea of the

eye.eye.• Adhesion proteinsAdhesion proteins—(fibronectin, laminin, collagen, fibrinogen) —(fibronectin, laminin, collagen, fibrinogen)

interact with receptors on plasma membranes to anchor cells in interact with receptors on plasma membranes to anchor cells in position and provide traction for cell movement.position and provide traction for cell movement.

CONNECTIVE TISSUE MATRIXCONNECTIVE TISSUE MATRIX FibersFibers

Synthesized by fibroblasts. Provide strength and support for Synthesized by fibroblasts. Provide strength and support for tissues.tissues.

• Collagen fibersCollagen fibers—at least five different types. Very tough and —at least five different types. Very tough and resistant to pulling forces, yet allow some flexibility in the tissue. resistant to pulling forces, yet allow some flexibility in the tissue. Often occur in bundles composed of many tiny fibrils lying parallel to Often occur in bundles composed of many tiny fibrils lying parallel to each other. Bundle arrangement provides great strength. each other. Bundle arrangement provides great strength. Composed of the protein Composed of the protein collagencollagen (most abundant protein in the (most abundant protein in the body). Found in most CT types—especially bone, cartilage, body). Found in most CT types—especially bone, cartilage, tendons, and ligaments.tendons, and ligaments.

• Elastic fibersElastic fibers—smaller diameter than collagen fibers. Branch and —smaller diameter than collagen fibers. Branch and join together to form a network within a tissue. Composed of the join together to form a network within a tissue. Composed of the protein protein elastinelastin and the large glycoproteins (especially and the large glycoproteins (especially fibrillinfibrillin). ). Provide strength. Can be stretched up to 150% of their relaxed Provide strength. Can be stretched up to 150% of their relaxed length without breaking. Plentiful in skin, blood vessel walls, and length without breaking. Plentiful in skin, blood vessel walls, and lung tissue.lung tissue.

• Reticular fibersReticular fibers—consist of —consist of collagencollagen and a glycoprotein coating. and a glycoprotein coating. Much thinner that collagen fibers and form a branching network. Much thinner that collagen fibers and form a branching network. Provide support in blood vessel walls. Form a network around fat Provide support in blood vessel walls. Form a network around fat cells, nerve fibers, and skeletal and smooth muscle cells. Provide cells, nerve fibers, and skeletal and smooth muscle cells. Provide support and strength and form the support and strength and form the stromastroma (supporting framework) (supporting framework) of many soft organs (spleen, lymph nodes). Help form basement of many soft organs (spleen, lymph nodes). Help form basement membrane.membrane.

TYPES OF CONNECTIVE TISSUE TYPES OF CONNECTIVE TISSUE (EMBRYONIC)(EMBRYONIC)

MesenchymeMesenchyme Description: Irregularly shaped mesenchymal cells Description: Irregularly shaped mesenchymal cells

embedded in a semifluid ground substance that embedded in a semifluid ground substance that contain delicate reticular fibers.contain delicate reticular fibers.

Location: Deep to skin, along developing embryonic Location: Deep to skin, along developing embryonic bones. Some mesenchymal cells found in adult CT—bones. Some mesenchymal cells found in adult CT—especially along blood vessels.especially along blood vessels.

Function: Forms all other kinds of CT.Function: Forms all other kinds of CT. Mucous connective tissueMucous connective tissue

Description: Star-shaped cells embedded in a Description: Star-shaped cells embedded in a viscous, jellylike ground substance that contain fine viscous, jellylike ground substance that contain fine collagen fibers.collagen fibers.

Location: Umbilical cord.Location: Umbilical cord. Function: Support.Function: Support.

TYPES OF CONNECTIVE TISSUETYPES OF CONNECTIVE TISSUE Areolar connective tissueAreolar connective tissue

Description: Fibers (collagen, elastic, and reticular) and Description: Fibers (collagen, elastic, and reticular) and several kinds of cells (fibroblasts, macrophages, plasma several kinds of cells (fibroblasts, macrophages, plasma cells, adipocytes, and mast cells) embedded in a semifluid cells, adipocytes, and mast cells) embedded in a semifluid ground substance.ground substance.

Location: Subcutaneous layer of skin, papillary (superficial) Location: Subcutaneous layer of skin, papillary (superficial) region of dermis of skin, mucous membranes, blood vessels, region of dermis of skin, mucous membranes, blood vessels, nerves, and around body organs.nerves, and around body organs.

Function: Strength, elasticity, support.Function: Strength, elasticity, support.

TYPES OF CONNECTIVE TISSUETYPES OF CONNECTIVE TISSUE Adipose tissueAdipose tissue

Description: Consists of adipocytes, specialized cells that store Description: Consists of adipocytes, specialized cells that store triglycerides (fats and oils) in a large central area. Nuclei are triglycerides (fats and oils) in a large central area. Nuclei are peripherally located.peripherally located.

Location: Subcutaneous skin layer, around heart and kidneys, yellow Location: Subcutaneous skin layer, around heart and kidneys, yellow bone marrow of long bones, padding around joints, and behind eyeball in bone marrow of long bones, padding around joints, and behind eyeball in eye socket.eye socket.

Function: Heat regulation, energy reserve, support and protection. In Function: Heat regulation, energy reserve, support and protection. In newborns, brown fat generates heat to help maintain body temperature.newborns, brown fat generates heat to help maintain body temperature.

TYPES OF CONNECTIVE TISSUETYPES OF CONNECTIVE TISSUE Reticular connective tissueReticular connective tissue

Description: Network of interlacing reticular fibers and Description: Network of interlacing reticular fibers and reticular cells.reticular cells.

Location: Stroma (framework) of liver, spleen, lymph nodes. Location: Stroma (framework) of liver, spleen, lymph nodes. Red bone marrow that gives rise to blood cells. Reticular Red bone marrow that gives rise to blood cells. Reticular lamina of basement membrane.lamina of basement membrane.

Function: Forms stroma of organs. Binds smooth muscle Function: Forms stroma of organs. Binds smooth muscle tissue cells together.tissue cells together.

TYPES OF CONNECTIVE TISSUETYPES OF CONNECTIVE TISSUE Dense regular connective tissue:Dense regular connective tissue:

Description: Matrix has shiny white appearance. Mostly Description: Matrix has shiny white appearance. Mostly composed of collagen fibers arranged in parallel bundles. composed of collagen fibers arranged in parallel bundles. Fibroblasts present in rows between bundles.Fibroblasts present in rows between bundles.

Location: Tendons, most ligaments, and aponeuroses Location: Tendons, most ligaments, and aponeuroses (sheetlike tendons that attach muscle to other muscle or (sheetlike tendons that attach muscle to other muscle or bones).bones).

Function: Provides strong attachment between various Function: Provides strong attachment between various structures.structures.

TYPES OF CONNECTIVE TISSUETYPES OF CONNECTIVE TISSUE Dense irregular connective tissueDense irregular connective tissue

Description: Predominantly collagen fibers, randomly arranged, Description: Predominantly collagen fibers, randomly arranged, and a few fibroblasts. Usually forms a sheet.and a few fibroblasts. Usually forms a sheet.

Location: Fascia, reticular (deeper) region of dermis of skin, Location: Fascia, reticular (deeper) region of dermis of skin, perichondrium (membrane around cartilage), periosteum perichondrium (membrane around cartilage), periosteum (membrane around bone), joint capsules, dura mater (outer (membrane around bone), joint capsules, dura mater (outer membrane around brain and spinal cord), membrane capsules membrane around brain and spinal cord), membrane capsules around various organs, heart valves.around various organs, heart valves.

Function: Provides strength.Function: Provides strength. Elastic connective tissueElastic connective tissue

Description: Predominantly freely branching elastic fibers. Description: Predominantly freely branching elastic fibers. Fibroblasts present in spaces between fibers.Fibroblasts present in spaces between fibers.

Location: Lung tissue, walls of elastic arteries, trachea, bronchial Location: Lung tissue, walls of elastic arteries, trachea, bronchial tubes, true vocal cords, suspensory ligament of penis, and tubes, true vocal cords, suspensory ligament of penis, and ligamenta flava of vertebrae (ligaments between vertebrae).ligamenta flava of vertebrae (ligaments between vertebrae).

Function: Allows stretching of various organs.Function: Allows stretching of various organs.

TYPES OF CONNECTIVE TISSUETYPES OF CONNECTIVE TISSUE Hyaline cartilageHyaline cartilage

Description: Bluish-white, shiny ground substance with fine Description: Bluish-white, shiny ground substance with fine collagen fibers. Contains numerous chondrocytes. Most collagen fibers. Contains numerous chondrocytes. Most abundant type of cartilage.abundant type of cartilage.

Location: Ends of long bones, anterior ends of ribs, nose, Location: Ends of long bones, anterior ends of ribs, nose, parts of larynx, trachea, bronchi, bronchial tubes, embryonic parts of larynx, trachea, bronchi, bronchial tubes, embryonic skeleton.skeleton.

Function: Provides smooth surfaces for movement at joints, Function: Provides smooth surfaces for movement at joints, flexibility, and support.flexibility, and support.

TYPES OF CONNECTIVE TISSUETYPES OF CONNECTIVE TISSUE FibrocartilageFibrocartilage

Description: Chondrocytes scattered among bundles Description: Chondrocytes scattered among bundles of collagen fibers within the matrix.of collagen fibers within the matrix.

Location: Pubic symphysis, intervertebral discs, Location: Pubic symphysis, intervertebral discs, menisci (cartilage pads) of knees.menisci (cartilage pads) of knees.

Function: Support and fusion.Function: Support and fusion.

Elastic cartilageElastic cartilage Description: Chondrocytes located in a threadlike Description: Chondrocytes located in a threadlike

network of elastic fibers within the matrix.network of elastic fibers within the matrix. Location: Epiglottis of larynx, external ear, auditory Location: Epiglottis of larynx, external ear, auditory

(Eustacian) tubes.(Eustacian) tubes. Function: Support and shape maintenance.Function: Support and shape maintenance.

TYPES OF CONNECTIVE TISSUETYPES OF CONNECTIVE TISSUE

Bone (osseous) tissueBone (osseous) tissue Description: Description: Compact boneCompact bone consists of consists of osteonsosteons

(Haversian systems) that contain lamellae, lacunae, (Haversian systems) that contain lamellae, lacunae, osteocytes, canaliculi, and central (Haversian) canals. osteocytes, canaliculi, and central (Haversian) canals. Spongy boneSpongy bone consists of thin plates called consists of thin plates called trabeculaetrabeculae with red bone marrow between the with red bone marrow between the trabeculae.trabeculae.

Location: Both compact and spongy bone form the Location: Both compact and spongy bone form the various parts of the body’s bones.various parts of the body’s bones.

Function: Support, protection, storage, houses blood-Function: Support, protection, storage, houses blood-forming tissue, serves as levers that act with muscles forming tissue, serves as levers that act with muscles to provide body movement.to provide body movement.

TYPES OF CONNECTIVE TISSUETYPES OF CONNECTIVE TISSUE

Bone (osseous) tissueBone (osseous) tissue

TYPES OF CONNECTIVE TISSUETYPES OF CONNECTIVE TISSUE

Blood (vascular tissue)Blood (vascular tissue) Description: Plasma and formed elements. Formed Description: Plasma and formed elements. Formed

elements are erythrocytes (red blood cells), elements are erythrocytes (red blood cells), leukocytes (white blood cells), and platelets.leukocytes (white blood cells), and platelets.

Location: Within blood vessels (arteries, arterioles, Location: Within blood vessels (arteries, arterioles, capillaries, venules, and veins).capillaries, venules, and veins).

Function: Erythrocytes transport oxygen and carbon Function: Erythrocytes transport oxygen and carbon dioxide. Leukocytes are involved in phagocytosis, dioxide. Leukocytes are involved in phagocytosis, allergic reactions, and immunity. Platelets are allergic reactions, and immunity. Platelets are essential for blood clotting.essential for blood clotting.

TYPES OF CONNECTIVE TISSUETYPES OF CONNECTIVE TISSUE

Blood (vascular tissue)Blood (vascular tissue)

MEMBRANESMEMBRANES Epithelial membraneEpithelial membrane—The combination —The combination

of an epithelial layer and the underlying of an epithelial layer and the underlying connective tissue layer. Principal connective tissue layer. Principal epithelial membranes are:epithelial membranes are: Mucous membraneMucous membrane Serous membraneSerous membrane Cutaneous membraneCutaneous membrane—Skin. An organ of —Skin. An organ of

the integumentary system. Will be discussed the integumentary system. Will be discussed later.later.

Synovial membraneSynovial membrane—Contains —Contains connective tissue only—no epithelium.connective tissue only—no epithelium.

MUCOUS MEMBRANESMUCOUS MEMBRANES Line body cavities that open directly to the exterior Line body cavities that open directly to the exterior

(entire digestive, respiratory, and reproductive systems, (entire digestive, respiratory, and reproductive systems, and much of the urinary system).and much of the urinary system).

Consist of a lining layer of epithelium and an underlying Consist of a lining layer of epithelium and an underlying layer of connective tissuelayer of connective tissue

Epithelial layer provides barrier against microbes and Epithelial layer provides barrier against microbes and other pathogens, secretes mucus (moisturizes body other pathogens, secretes mucus (moisturizes body cavities, traps particles in the respiratory tract, and cavities, traps particles in the respiratory tract, and lubricates food), secretes enzymes digestive enzymes, lubricates food), secretes enzymes digestive enzymes, and is the site for food and fluid absorption in the GI and is the site for food and fluid absorption in the GI tract.tract.

Connective tissue layer is called the Connective tissue layer is called the lamina proprialamina propria. It . It binds the epithelium to underlying structures while binds the epithelium to underlying structures while allowing some flexibility, holds blood vessels in place, allowing some flexibility, holds blood vessels in place, and protects underlying muscles from abrasion or and protects underlying muscles from abrasion or puncture. Oxygen and nutrients diffuse from the lamina puncture. Oxygen and nutrients diffuse from the lamina propria to the epithelial layer while carbon dioxide and propria to the epithelial layer while carbon dioxide and wastes diffuse in the opposite direction.wastes diffuse in the opposite direction.

SEROUS MEMBRANESSEROUS MEMBRANES Line body cavities that do not open to the exterior and Line body cavities that do not open to the exterior and

cover the organs lying within those cavities.cover the organs lying within those cavities. Composed of two layers:Composed of two layers:

Parietal layerParietal layer—attached to the cavity wall.—attached to the cavity wall. Visceral layerVisceral layer—attached to and covering the organs within the —attached to and covering the organs within the

cavity.cavity. Epithelial layer secretes a watery fluid called Epithelial layer secretes a watery fluid called serous serous

fluidfluid, which allows organs to glide freely against each , which allows organs to glide freely against each other and against the cavity wall.other and against the cavity wall.

Epithelial layer is composed of mesothelium (simple Epithelial layer is composed of mesothelium (simple squamous epithelium).squamous epithelium).

Connective tissue layer is composed of a thin layer of Connective tissue layer is composed of a thin layer of areolar CT.areolar CT.

Serous membrane of the thoracic cavity is called the Serous membrane of the thoracic cavity is called the pleurapleura, of the pericardial cavity is the , of the pericardial cavity is the pericardiumpericardium, and , and of the abdominal cavity is the of the abdominal cavity is the peritoneumperitoneum..

SYNOVIAL MEMBRANESSYNOVIAL MEMBRANES

Do not contain epithelium.Do not contain epithelium. Line cavities that do not open to the exterior.Line cavities that do not open to the exterior. Line the cavities of freely movable joints, bursae Line the cavities of freely movable joints, bursae

(cushioning sacs), and tendon sheaths in our (cushioning sacs), and tendon sheaths in our hands and feet.hands and feet.

Composed of areolar CT, with elastic fibers and Composed of areolar CT, with elastic fibers and varying amounts of fat.varying amounts of fat.

Secrete Secrete synovial fluidsynovial fluid, which lubricates the , which lubricates the cartilage at the end of bones during movement cartilage at the end of bones during movement and nourishes the cartilage at joints.and nourishes the cartilage at joints.

MUSCLE TISSUEMUSCLE TISSUE

Muscle tissue consists of fibers (cells) that Muscle tissue consists of fibers (cells) that are designed to generate force for are designed to generate force for contraction. It provides motion, maintains contraction. It provides motion, maintains posture, and generates heat. Muscle posture, and generates heat. Muscle tissue is classified into three types, based tissue is classified into three types, based on location, structure, and function:on location, structure, and function: Skeletal muscle tissueSkeletal muscle tissue Cardiac muscle tissueCardiac muscle tissue Smooth muscle tissueSmooth muscle tissue

TYPES OF MUSCLE TISSUETYPES OF MUSCLE TISSUE Skeletal muscle tissueSkeletal muscle tissue

Description: Long, cylindrical, striated (having alternating Description: Long, cylindrical, striated (having alternating light and dark bands) fibers with many peripherally located light and dark bands) fibers with many peripherally located nuclei. Voluntary control (can be made to contract or relax nuclei. Voluntary control (can be made to contract or relax by conscious control).by conscious control).

Location: Usually attached to bones by tendons.Location: Usually attached to bones by tendons. Function: Motion, posture, heat production (thermogenesis).Function: Motion, posture, heat production (thermogenesis).

TYPES OF MUSCLE TISSUETYPES OF MUSCLE TISSUE Cardiac muscle tissueCardiac muscle tissue

Description: Branched, striated fibers with one or two Description: Branched, striated fibers with one or two centrally located nuclei. Contains centrally located nuclei. Contains intercalated discsintercalated discs (unique end-to-end attachments between muscle fibers). (unique end-to-end attachments between muscle fibers). Involuntary control (contractions are usually not under Involuntary control (contractions are usually not under conscious control).conscious control).

Location: Heart wall.Location: Heart wall. Function: Pumps blood to all parts of the body.Function: Pumps blood to all parts of the body.

TYPES OF MUSCLE TISSUETYPES OF MUSCLE TISSUE Smooth muscle tissueSmooth muscle tissue

Description: Spindle-shaped, nonstriated (smooth) fibers with one Description: Spindle-shaped, nonstriated (smooth) fibers with one centrally located nucleus. Usually involuntary control. centrally located nucleus. Usually involuntary control.

Location: Walls of hollow internal structures such as blood vessels, Location: Walls of hollow internal structures such as blood vessels, airways to the lungs, stomach, intestines, gallbladder, urinary bladder, airways to the lungs, stomach, intestines, gallbladder, urinary bladder, and ureters.and ureters.

Function: Motion (constriction of blood vessels/airways, propulsion of Function: Motion (constriction of blood vessels/airways, propulsion of food through GI tract, contraction of urinary bladder/gallbladder).food through GI tract, contraction of urinary bladder/gallbladder).

NERVOUS TISSUENERVOUS TISSUE Composed of only two principal cell types:Composed of only two principal cell types:

NeuronsNeurons—Nerve cells. Convert stimuli into nerve —Nerve cells. Convert stimuli into nerve impulses, which they conduct to other neurons, impulses, which they conduct to other neurons, muscle tissue, or glands. Most neurons consist of:muscle tissue, or glands. Most neurons consist of:

• Cell bodyCell body—contains the nucleus and other typical —contains the nucleus and other typical organelles.organelles.

• DendritesDendrites—tapering, highly branched, usually short —tapering, highly branched, usually short extensions that are the major input receiving portions of extensions that are the major input receiving portions of neurons.neurons.

• AxonAxon—single, thin, cylindrical process that may be very —single, thin, cylindrical process that may be very long. Output portion of a neuron—conducts nerve impulses long. Output portion of a neuron—conducts nerve impulses toward another neuron or other tissue.toward another neuron or other tissue.

NeurogliaNeuroglia—Do not generate or conduct nerve —Do not generate or conduct nerve impulses but do perform many important support impulses but do perform many important support functions in nervous tissue.functions in nervous tissue.

NERVOUS TISSUENERVOUS TISSUE

Description: Consists of Description: Consists of neurons and neuroglia.neurons and neuroglia.

Location: Nervous system.Location: Nervous system. Function: Exhibits sensitivity Function: Exhibits sensitivity

to various stimuli, converts to various stimuli, converts stimuli into nerve impulses, stimuli into nerve impulses, and conducts nerve impulses and conducts nerve impulses to other neurons, muscle to other neurons, muscle fibers, or glands.fibers, or glands.