HistologyHistologyCell Biology ReviewCell Biology Review

And And

HistologyHistology

ObjectivesObjectives

• List the 4 major types of tissues of the List the 4 major types of tissues of the human body.human body.

• Describe the characteristics, cell types, Describe the characteristics, cell types, function, and the location of epithelial function, and the location of epithelial tissues.tissues.

• Describe the characteristics, cell types, Describe the characteristics, cell types, functions, and the location of connective functions, and the location of connective tissues.tissues.

• Describe the characteristics, cell types, Describe the characteristics, cell types, functions, and the location of muscle functions, and the location of muscle tissues.tissues.

• Describe the characteristics, cell types, Describe the characteristics, cell types, functions, and the location of nervous functions, and the location of nervous tissues.tissues.

True TissuesTrue Tissues

• A tissue is a group of like cells of A tissue is a group of like cells of similar specialized structure which similar specialized structure which carryout specific functions.carryout specific functions.

• Groups of tissues compose and work Groups of tissues compose and work together to form organs. together to form organs. All organs All organs are composed of two or more types of are composed of two or more types of tissuestissues..

• There are four major tissue types:There are four major tissue types:a. Epitheliala. Epithelialb. Connectiveb. Connectivec. Musclec. Muscled. Nervousd. Nervous

Epithelial TissueEpithelial Tissue• Epithelial tissues are tissues that are found on the Epithelial tissues are tissues that are found on the

outer surface or linings of internal cavities and outer surface or linings of internal cavities and organs. They are also found in many glands and organs. They are also found in many glands and produce materials that are secreted by the glands produce materials that are secreted by the glands (skin, lining of trachea, esophagus, urinary bladder, (skin, lining of trachea, esophagus, urinary bladder, and digestive tract, sweat glands, kidneys).and digestive tract, sweat glands, kidneys).

• These cells are rapidly dividing because they are These cells are rapidly dividing because they are constantly being sloughed away or rubbed off. constantly being sloughed away or rubbed off. Therefore they must constantly be replaced.Therefore they must constantly be replaced.

• They all have a lower layer which consists of germ They all have a lower layer which consists of germ cells that are constantly dividing producing new cells that are constantly dividing producing new cells.cells.

• They are all They are all avascularavascular, meaning they are without a , meaning they are without a direct blood supply. They are nourished by blood direct blood supply. They are nourished by blood vessels in the tissue layer below them.vessels in the tissue layer below them.

• They often contain gland cells which secrete They often contain gland cells which secrete lubricating substances such as mucous and form lubricating substances such as mucous and form mucous membranes (nose, mouth, urogenital tract) mucous membranes (nose, mouth, urogenital tract) and serosa membranes which form the outer and serosa membranes which form the outer covering of the digestive organs.covering of the digestive organs.

General Structural General Structural Characteristics of Epithelial Characteristics of Epithelial

Tissues:Tissues:• Epithelial tissues have Epithelial tissues have

three basic shapes:three basic shapes:a. a. SquamousSquamous- flattened - flattened cells, fried egg shape cells, fried egg shape in appearance.in appearance.b. b. CuboidalCuboidal- square or - square or cubed shaped. Cells cubed shaped. Cells are as wide as they are are as wide as they are tall.tall.c. c. ColumnarColumnar- cells are - cells are taller than they are taller than they are wide. Shaped like wide. Shaped like columns or rectangles.columns or rectangles.

General Structural General Structural Characteristics of Epithelial Characteristics of Epithelial

Tissues:Tissues:• Epithelial tissues are Epithelial tissues are

also classified also classified according to how many according to how many layers compose them.layers compose them.a. a. Simple epithelial Simple epithelial tissuestissues are only one are only one cell layer thick.cell layer thick.b. b. Stratified epithelialStratified epithelial tissues are several tissues are several layers thick.layers thick.c. c. Pseudostratified Pseudostratified epithelialepithelial appear to be appear to be composed of multiple composed of multiple layers but on close layers but on close examination is actually examination is actually only one layer thick.only one layer thick.

Naming Epithelial Naming Epithelial TissuesTissues• Epithelial tissues are named in the Epithelial tissues are named in the

following manner:following manner:First wordFirst word: Number of layers (simple, : Number of layers (simple, stratified, pseudostratified)stratified, pseudostratified)Second wordSecond word: Shape of cell : Shape of cell (squamous, cuboidal, columnar)(squamous, cuboidal, columnar)Third wordThird word: Describes the apical : Describes the apical surface if there are structures (cilia or surface if there are structures (cilia or microvilli) or materials present microvilli) or materials present (keratin).(keratin).From the name given you can tell much about the tissue. For example

pseudostratified columnar ciliated epithelial. What can you tell from the name about the tissue?

1. It is one cell- layer thick.2. It is column shaped.3. It has cilia.

Types of Epithelial Types of Epithelial TissuesTissues

• Simple squamousSimple squamous: : This type is found This type is found lining blood vessels lining blood vessels and is called and is called endotheliumendothelium. It is . It is also in the alveoli or also in the alveoli or airs of of the lungs. airs of of the lungs. This tissue allows This tissue allows the rapid exchange the rapid exchange of materials by of materials by diffusion and diffusion and osmosis from cell to osmosis from cell to cell. cell.

Types of Epithelial Types of Epithelial TissuesTissues

• Stratified squamousStratified squamous: : This type of This type of epithelium is present epithelium is present in areas where there in areas where there is wear and tear on is wear and tear on the tissue which are the tissue which are constantly having constantly having cells sloughed away or cells sloughed away or being rubbed off by being rubbed off by abrasion. There are abrasion. There are two types of stratified two types of stratified squamous. squamous. Keratinized and Non-Keratinized and Non-keratinized. keratinized. KeratinKeratin is a layer a is a layer a waterproof protein on waterproof protein on the apical surface of the apical surface of stratified squamous stratified squamous keratinized keratinized epithelium (skin). epithelium (skin).

Types of Epithelial Types of Epithelial TissuesTissues

• Stratified squamous: Stratified squamous Stratified squamous: Stratified squamous epithelial non-keratinizedepithelial non-keratinized lines the oral lines the oral cavity and the esophagus and the vagina cavity and the esophagus and the vagina of the female reproductive system.of the female reproductive system.

Types of Epithelial Types of Epithelial TissuesTissues

• Stratified squamousStratified squamous: : Stratified squamous Stratified squamous epthithelium keratinizedepthithelium keratinized KeratinKeratin is a is a layer a waterproof protein on the apical layer a waterproof protein on the apical surface of stratified squamous keratinized surface of stratified squamous keratinized epithelium (skin). epithelium (skin).

Types of Epithelial Types of Epithelial TissuesTissues

• Simple cuboidalSimple cuboidal: Simple cuboidal cells : Simple cuboidal cells are common in secretory glands and in are common in secretory glands and in the collecting tubules where they are the collecting tubules where they are involved with reabsorption of materials involved with reabsorption of materials as urine is being produced.as urine is being produced.

Types of Epithelial Types of Epithelial TissuesTissues• Simple columnarSimple columnar: Simple columnar is located in : Simple columnar is located in

various areas of the body. It is commonly found in the various areas of the body. It is commonly found in the lining of the small and large intestine where it is lining of the small and large intestine where it is involved with absorption of molecules from digested involved with absorption of molecules from digested food and re-absorption of water. In the small intestine food and re-absorption of water. In the small intestine the apical surface of these cells have the apical surface of these cells have microvillimicrovilli present present on their surface and specialized gland cells called on their surface and specialized gland cells called goblet cellsgoblet cells which produce and secrete mucus. which produce and secrete mucus.

microvilli on apical surface

Types of Epithelial Types of Epithelial TissuesTissues

• Pseudostratified columnar ciliatedPseudostratified columnar ciliated:: This tissue This tissue appears to be stratified but is actually one layer of appears to be stratified but is actually one layer of irregularly shaped cells. irregularly shaped cells. The apical surface of The apical surface of these cells have tiny, hair-like projections called these cells have tiny, hair-like projections called ciliacilia, which are involved with the movement across , which are involved with the movement across the surface of the cells.the surface of the cells. This epithelial tissue also This epithelial tissue also has the mucus secreting goblet cells present. This has the mucus secreting goblet cells present. This tissue forms the lining of the trachea, bronchi, and tissue forms the lining of the trachea, bronchi, and lining of the Fallopian tubes (oviducts) of female.lining of the Fallopian tubes (oviducts) of female.

Types of Epithelial Types of Epithelial TissuesTissues• Stratified transitional:Stratified transitional: This epithelium This epithelium

is unique to the urinary bladder and a is unique to the urinary bladder and a small portion of the ureters. small portion of the ureters. It has the It has the unique property of expansion and unique property of expansion and contraction.contraction. This allows the tissue to This allows the tissue to adjust to the urinary bladder’s expansion adjust to the urinary bladder’s expansion and contraction when it is full or empty.and contraction when it is full or empty.

Connective TissuesConnective Tissues• Connective tissues get there name because Connective tissues get there name because

they attach different or hold different tissue they attach different or hold different tissue types together.types together.

• They all are composed of cells which produce They all are composed of cells which produce materials which they secrete or release in materials which they secrete or release in their extracellular space to form extracellular their extracellular space to form extracellular matrixmatrix. The matrix is non-living!. The matrix is non-living!

• The matrix varies depending on the The matrix varies depending on the connective tissue type. Some matrices are connective tissue type. Some matrices are hard, solid, crystalline structure (bones), hard, solid, crystalline structure (bones), some flexible (cartilages), some composed of some flexible (cartilages), some composed of protein fibers (tendons and ligaments), some protein fibers (tendons and ligaments), some sponge-like rich in fluid (dermis of skin), soft sponge-like rich in fluid (dermis of skin), soft (adipose), or liquid (plasma of blood(adipose), or liquid (plasma of blood).).

• Often the cells are very scattered about and Often the cells are very scattered about and few in number. This is why some connective few in number. This is why some connective tissues take long periods of time to heal tissues take long periods of time to heal when damaged (cartilage and bone).when damaged (cartilage and bone).

Connective Tissue TypesConnective Tissue Types• Loose irregular connective: AreaolarLoose irregular connective: Areaolar tissue has a tissue has a

gel like matrix with cells called gel like matrix with cells called fibroblastfibroblast which which produce two types of protein fibers, produce two types of protein fibers, collagencollagen (larger) and (larger) and elastinelastin (small thread-like). It is (small thread-like). It is located around the organs, under mucus located around the organs, under mucus membrane epithelial and surrounding capillaries. membrane epithelial and surrounding capillaries. Holds and conveys tissue fluid. Holds and conveys tissue fluid.

Connective Tissues TypesConnective Tissues Types• Loose reticular connectiveLoose reticular connective: Has a network of : Has a network of

protein protein reticular fibersreticular fibers. These fibers form a soft . These fibers form a soft internal skeleton that support other cell types, internal skeleton that support other cell types, particularly erythrocytes (red blood cells) and particularly erythrocytes (red blood cells) and leukocytes (white blood cells). This tissue compose leukocytes (white blood cells). This tissue compose the spleen, lymph nodes, and bone marrow.the spleen, lymph nodes, and bone marrow.

Connective Tissues TypesConnective Tissues Types• Adipose connective tissueAdipose connective tissue: Matrix composed of collagen : Matrix composed of collagen

and elastin fibers but very sparse and closely packed and elastin fibers but very sparse and closely packed together. together. AdipocyteAdipocytes (fat cells) are present. They are s (fat cells) are present. They are large cells with their nuclei pushed to the side by large large cells with their nuclei pushed to the side by large fat droplets which are centrally located. Provides energy fat droplets which are centrally located. Provides energy storage, insulation, support and protection to internal storage, insulation, support and protection to internal organs. Located under the skin, around the kidneys, organs. Located under the skin, around the kidneys, heart, within the abdomen and breasts of females.heart, within the abdomen and breasts of females.

Connective Tissues TypesConnective Tissues TypesAdipose Tissue DistributionAdipose Tissue Distribution

Connective Tissues TypesConnective Tissues Types• Dense regular connective:Dense regular connective: Composed primarily of Composed primarily of

parallel collagen fibers tightly packed together. parallel collagen fibers tightly packed together. Some elastin fibers are present. Some elastin fibers are present. FibroblastFibroblast cells are cells are present and form the fibers. Attaches muscles to present and form the fibers. Attaches muscles to bone or muscles to muscles. Can withstand great bone or muscles to muscles. Can withstand great pulling force when it is applied in one direction. pulling force when it is applied in one direction. Composes ligaments, tendons, and aponeuroses. Composes ligaments, tendons, and aponeuroses.

Connective Tissues TypesConnective Tissues Types• Dense irregular connectiveDense irregular connective: Matrix is primarily : Matrix is primarily

composed of collagen and elastin fibers irregularly composed of collagen and elastin fibers irregularly arranged (not parallel). Fibroblast are the cells arranged (not parallel). Fibroblast are the cells present and produce the matrix. This tissue is able present and produce the matrix. This tissue is able to withstand tension or stress exerted in many to withstand tension or stress exerted in many directions. It also provides structural strength. It directions. It also provides structural strength. It is located in the dermis of the skin, the submucosa is located in the dermis of the skin, the submucosa of the digestive tract and the fibrous capsules of the digestive tract and the fibrous capsules surrounding certain joints and organs. surrounding certain joints and organs.

Connective Tissues TypesConnective Tissues TypesCartilagesCartilages

• Cartilage is a connective tissue which has Cartilage is a connective tissue which has qualities between dense connective tissue qualities between dense connective tissue and bone.and bone.

• It is avascular and lacks nerve fibers.It is avascular and lacks nerve fibers.• The cells called The cells called chondroblastchondroblast secrete the secrete the

matrix. When the cells mature they are matrix. When the cells mature they are trapped within trapped within cavities called cavities called lacunaelacunae. . These mature cells surrounded by matrix These mature cells surrounded by matrix are called are called chondrocyteschondrocytes..

• There are three types of cartilages and they There are three types of cartilages and they differ in the composition of their matrix. differ in the composition of their matrix. They areThey are hyaline cartilage , elastic hyaline cartilage , elastic cartilage, and fibrocartilagecartilage, and fibrocartilage..

Connective Tissues TypesConnective Tissues Types• Hyaline cartilageHyaline cartilage: The matrix is amorphous : The matrix is amorphous

( without any particular shape) with a network of ( without any particular shape) with a network of collagen fibers present that are not visible. Its collagen fibers present that are not visible. Its functions are support, reinforcement, cushioning, functions are support, reinforcement, cushioning, resists compressive stress. It is located at the end of resists compressive stress. It is located at the end of long bones, form the cartilages of the rib cage, nose, long bones, form the cartilages of the rib cage, nose, trachea, and larynx (Adam’s apple). In a young child trachea, and larynx (Adam’s apple). In a young child the majority of the appendicular skeleton is the majority of the appendicular skeleton is composed of this type of cartilage which is eventually composed of this type of cartilage which is eventually replaced by bone tissue as the child matures.replaced by bone tissue as the child matures.

Connective Tissues TypesConnective Tissues Types• Elastic cartilageElastic cartilage: The matrix is similar to : The matrix is similar to

hyaline cartilage but the matrix is rich in hyaline cartilage but the matrix is rich in elastin fibers which are visible and usually elastin fibers which are visible and usually stain dark purple. This cartilage maintains stain dark purple. This cartilage maintains the shape of a structure while allowing the shape of a structure while allowing great flexibility. It is located in the pinna great flexibility. It is located in the pinna (outer ear) and the epiglottis of the throat.(outer ear) and the epiglottis of the throat.

Connective Tissues TypesConnective Tissues Types• FibrocartilageFibrocartilage: The matrix of this cartilage is : The matrix of this cartilage is

less firm than that of hyaline cartilage and less firm than that of hyaline cartilage and has many thick, visible collagen fibers has many thick, visible collagen fibers present.present.

This tissue functions in the absorption of This tissue functions in the absorption of compressive shock. It is located compressive shock. It is located intervertebral discs, the knee and the pubic intervertebral discs, the knee and the pubic symphysis.symphysis.

Connective Tissues TypesConnective Tissues Types• Bone or Osseous tissue:Bone or Osseous tissue:

Bone tissue matrix is Bone tissue matrix is secreted by cells called secreted by cells called osteoblastsosteoblasts. The matrix . The matrix is composed of collagen is composed of collagen fibers and calcium fibers and calcium (hydroxyapeptite (hydroxyapeptite crystals). The bone crystals). The bone matrix is constantly matrix is constantly being broken and being broken and reabsorbed by cells called reabsorbed by cells called osteoclastsosteoclasts. The cells . The cells which are in the lacunae which are in the lacunae and surrounded by the and surrounded by the matrix are called matrix are called osteocytesosteocytes. The bone . The bone tissue is highly tissue is highly vascularized and has vascularized and has nerve fibers present. The nerve fibers present. The blood vessels and nerve blood vessels and nerve supply are located in supply are located in tunnel like structures tunnel like structures which run through the which run through the matrix called matrix called Harversian Harversian CanalsCanals..

Connective Tissues TypesConnective Tissues Types

• Bone or osseous Bone or osseous tissuetissue: Bone tissue : Bone tissue functions are support, functions are support, protection, provides protection, provides levers to which levers to which muscles act on to muscles act on to produce movement, produce movement, storage of calcium, storage of calcium, phosphorous, and phosphorous, and other mineral, and other mineral, and the marrow inside the the marrow inside the bone is the site of bone is the site of blood cell production.blood cell production.

Connective Tissues TypesConnective Tissues Types• BloodBlood: Blood is composed of : Blood is composed of

formed elementsformed elements (cells) (cells) suspended in a suspended in a fluid matrix fluid matrix called called plasmaplasma. There are . There are three types of formed three types of formed elements, each with a specific elements, each with a specific function. function. ErythrocyteErythrocytes or red s or red blood cellsblood cells function in the function in the transport of oxygen. transport of oxygen. LeukocytesLeukocytes or white blood or white blood cellcell are involved with our are involved with our body’s defense against body’s defense against infection. infection. Thrombocytes Thrombocytes or or plateletsplatelets are actually are actually fragments of cells which are fragments of cells which are involved in blood clot involved in blood clot formation to prevent blood formation to prevent blood loss.loss.

• The bloods major functions The bloods major functions are the transport of nutrients are the transport of nutrients and the removal of waste and the removal of waste from the body’s tissues.from the body’s tissues.

Muscular TissueMuscular Tissue• Muscle tissue is composed of cells which Muscle tissue is composed of cells which

have the ability to contract (shorten) and have the ability to contract (shorten) and relax (lengthen).relax (lengthen).

• Muscle tissue is highly vascularized and Muscle tissue is highly vascularized and dense tissue.dense tissue.

• Muscle tissue can not regenerate itself Muscle tissue can not regenerate itself once it has been destroyed.once it has been destroyed.

• Muscle cells are called muscle fibers.Muscle cells are called muscle fibers.• There are three types of muscle tissues:There are three types of muscle tissues:

a. Striated or skeletal musclea. Striated or skeletal muscleb. Cardiac muscle or myocardial b. Cardiac muscle or myocardial

tissuetissuec. Smooth or visceral musclec. Smooth or visceral muscle

Muscular Tissue TypesMuscular Tissue Types• Striated or skeletal muscleStriated or skeletal muscle: This muscle is : This muscle is

composed of long, cylindrical, parallel fibers. composed of long, cylindrical, parallel fibers. There are bands or There are bands or striationsstriations present which run present which run across the width of the fiber. These fibers are across the width of the fiber. These fibers are multinucleatedmultinucleated (more than one nucleus present (more than one nucleus present per cell). This type of muscle tissue is under per cell). This type of muscle tissue is under conscious or voluntary control. This muscle has conscious or voluntary control. This muscle has the greatest strength of contraction but tires most the greatest strength of contraction but tires most rapidly. It functions are locomotion and facial rapidly. It functions are locomotion and facial expressions.expressions.

Muscular Tissue TypesMuscular Tissue Types• Cardiac muscleCardiac muscle: Cardiac muscle fibers are branched : Cardiac muscle fibers are branched

at the end with striations present, usually only one at the end with striations present, usually only one nucleus is present per cell. The branches of each nucleus is present per cell. The branches of each fiber come into contact at specialized junctions called fiber come into contact at specialized junctions called intercalated discsintercalated discs. It is involuntarily controlled by . It is involuntarily controlled by the autonomic nervous system and hormones. Its the autonomic nervous system and hormones. Its contractions are short, but the muscle fibers are contractions are short, but the muscle fibers are constantly contracting. Its function is to create the constantly contracting. Its function is to create the pump which propels the blood throughout the body.pump which propels the blood throughout the body.

Muscular Tissue TypesMuscular Tissue Types• Smooth or visceral muscle:Smooth or visceral muscle: These cells are spindle- These cells are spindle-

shaped (tapered on the ends) and lack striations. shaped (tapered on the ends) and lack striations. They have one nucleus present. They produce They have one nucleus present. They produce weaker contractions, however they contract for weaker contractions, however they contract for extended periods of time. They are involuntarily extended periods of time. They are involuntarily controlled by the autonomic nervous system or controlled by the autonomic nervous system or hormones. They are found in the digestive organs, hormones. They are found in the digestive organs, arteries and veins, the trachea and bronchiole tubes, arteries and veins, the trachea and bronchiole tubes, and the urogenital tract. Their contractions propels and the urogenital tract. Their contractions propels or moves substances or objects from one location to or moves substances or objects from one location to another.another.

Nervous TissueNervous Tissue• These tissues have the ability of These tissues have the ability of

excitability. They respond to excitability. They respond to environmental stimuli.environmental stimuli.

• They relay messages in the form of They relay messages in the form of electrical and chemical signals.electrical and chemical signals.

• They do not have the ability to regenerate They do not have the ability to regenerate when damaged.when damaged.

• They can reach great lengths even though They can reach great lengths even though they are microscopicthey are microscopic

• There are two major cell types:There are two major cell types:1. 1. NeuronsNeurons which relay the message. which relay the message.

2. 2. Neuroglial cellsNeuroglial cells which insulate which insulate and support and support

the neurons.the neurons.

Nervous TissueNervous Tissue• Nervous tissue:Nervous tissue: This This

tissue composes the tissue composes the brain, spinal cord, brain, spinal cord, and the peripheral and the peripheral nervous system. nervous system. Transmit electrical Transmit electrical signals from sensory signals from sensory receptors to the receptors to the integration center integration center and then from the and then from the integration center to integration center to the effector organ.the effector organ.