Chapter 5 - Lecture notes 5 PDF

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Cells are organized into tissues ● Some cells in the body are separated from each other in fluid filled spaces or intercellular spaces ○ E.g. blood cells ● Many other cell types are tightly packed with structures called intercellular junctions that connect their cell membranes Types of intercellular junctions ● Tight junctions: closed space between cells by fusing cell membranes ○ Cells that line the small intestine ● Desmosomes: bind cells by forming " spot wields" between cell membranes ○ Cells of the outer skin layer ● Gap junctions: form tubular channels between cells ○ Muscle cells of the heart and digestive tract Tissues are three dimensional structures in the body Four Major Types of Tissue ● Epithelial ○ Protection, secretion, absorption, excretion ○ Cover body surface and line organs, compose glands ○ Lack blood vessels ○ Cells divide and tightly packed ● Connective ○ Bind, support, protect, fill spaces, store fats, produces blood cells ○ Widely distributed throughout the body ○ Mostly have good blood supply, farther apart, extracellular mix ● Muscle ○ Movement ○ Attached to bones in the walls of organs ○ Able to contract in response to specific stimuli ● Nervous ○ Conduct impulses for coordination, regulation, integration ○ Brain, spinal cord, nerves ○ Cells communicate with each other and other body parts Epithelial Tissues ● Always has a free (apical) surface exposed to the outside or internally to an open space ● A thin, extracellular layer, called the basement membrane anchors, epithelium to under lying connective tissues ● Simple squamous epithelium ○ Consists of a single layer of thin, flattened cells ○ Fit tightly together and their nuclei are usually broad and thin ○ Is common at sites of diffusion and filtration ○ Lines the air sacs (alveoli) of the lungs where oxygen and CO2 are exchanged

Forms walls of the capillaries, lines the insides of blood and lymph vessels, and is part of the membranes that line body cavities and cover the viscera ○ Easily damaged Simple cuboidal epithelium ○ Consists of a single layer of cube shaped cells ○ Most cells have centrally located spherical nuclei ○ Lines the follicles of the thyroid gland, covers the ovaries, lines the kidney tubules and ducts of certain glands where the free surface faces the hollow channel of lumen ○ In the kidneys, it functions in tubular secretion and tubular reabsorption ○ In glands, it secretes glandular products Simple Columnar Epithelium ○ Composed of a single layer of cells that are longer than they are wide ○ Whose nuclei are typically at the same level, near the basement membrane ○ Cells can be ciliated or non-ciliated ○ Motile cilia extend from the free surfaces of the cells and they move constantly ○ Non-ciliated lines the uterus and some of the digestive tract (stomach, small and large intestines) ○ Tissue is thick, enabling to protect underlying tissues ○ Secretes digestive fluids and absorbs nutrients from digested food ○ Cells specialized for absorption typically have many tiny, cylindrical processes, called microvilli ○ Microvilli increase the surface area of cell membrane ○ Goblet cells ■ Specialized flask-shaped glandular cells that are scattered among others ■ Secrete a protective fluid (mucus) Pseudostratified columnar epithelium ○ Cells appear stratified or layered, but they are not ○ This affect occurs because the nuclei are at two or more levels in the row of aligned cells ○ All reach the basement membrane while some don’t reach the free surface ○ Commonly have cilia, which extend from their free surfaces ○ Lines the passages of the respiratory system (nasal and bronchial tree) Stratified squamous epithelium ○ Consists of many layers of cells, make this tissue relatively thick ○ From top to bottom, very flat to cuboidal or columnar shaped ○ Superficial portion of the skin (epidermis) ○ As the older cells are pushed outward, they accumulate proteins called keratins, then harden and die ○ Lines the oral cavity (pharynx, esophagus, thorax) Stratified cuboidal epithelium ○ Consists of two or three layers of cuboidal cells that form lining of a lumen ○ Lines the ducts of the mammary glands, sweat glands, salivary glands, and pancreas Stratified columnar epithelium ○ Consists of several layers of cells ○

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○ Superficial cells are elongated ○ The basal layers consists of cuboidal cells ○ Found in male urethra and lining of the larger ducts of exocrine cells Transitional epithelium ○ Specialized to change in response to increased tension ○ Forms the inner lining of the urinary bladder and lines the uterus and urethra ○ When the organs contract, there are several layers of irregular shaped cells ○ When the organ is distended, the tissues stretches and the cells elongate ○ Forms a barrier that helps prevent the contents of the urinary tract from offspring back into the internal environment Glandular epithelium ○ Composed of cells specialized to produce and secrete substances into ducts or into body fluids ○ Exocrine glands: glands that secrete their products into ducts that open onto surfaces, such as the skin or the lining of the digestive tract ■ Unicellular glands: a single secretory cell ■ Multi-cellular glands: glands that consist of many cells ■ Simple glands: glands that communicate with surface by ducts that do not branch ■ Simple-tubular glands: straight tube-like gland that opens directly onto surface ○ Endocrine glands: glands that secrete their products into tissue fluid or blood ○ Simple gland: communicates with the surface by means of a duct that does not branch before reaching the glandular cells or secreting portions ○ Compound glands: has a duct that branches repeatedly before reaching the secretory portion ○ Tubular glands: saclike dilations ○ Merocrine glands: glands that release fluid products by exocytosis ○ Apocrine glands: glands that lose small portions of their glandular cell bodies during secretion ○ Holocrine glands: glands that release entire cells ○ Serous fluid: watery or slippery fluid that lubricates ○ Mucus: thicker fluid is rich in the glycoprotein mucin ■ Mucus cells and goblet cells secrete mucus

Connective Tissue ● The most abundant type of tissue by weight ● They bind structures, provide support and protection, serve as frameworks, fill spaces, store fat, produce blood cells, protect against infections, and help repair tissue damage ● Has an abundant of extracellular matrix between the cells ● Extracellular matrix is composed of protein fibers and a ground substance consisting of non-fibrous protein and fluid ○ Can be solid or flexible (bone and cartilage) ● Most cells can divide

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Major cell types ○ Fixed cells: cells that reside in the specific connective tissue type or an extended period ■ Includes fibroblasts and mast cells ○ Wandering cells: cells that move through and appear in tissues temporarily, usually in response to an injury or infection ■ Includes macrophages ○ Fibroblasts: the most common type of fixed cell in connective tissue ■ Large, star-shaped cells produce fibers by secretary proteins into the extracellular matrix of connective tissues ○ Macrophages: or histiocytes, originate as white blood cells and they are usually attached to fibers but can detach ■ Are specialized to carry on phagocytosis ■ Can clear foreign particles from tissues ○ Mast cells: release heparin, a compound that prevents blood clotting ■ Usually near blood vessels ■ Also release histamine, which promotes some of the reactions with inflammation and allergies Reticular Connective Tissue ○ Compound of thin, reticular fibers in a 3D network ○ Helps provide the framework of certain internal organs, such as the liver and spleen Dense regular connective tissue ○ Consists of many closely packed, thick collagen fibers; a fine network of elastic fibers; and a few cells mostly fibroblasts ○ Consists largely of tightly packed collagen fibers, which often binds tendons and ligaments ○ Blood supply is poor, slowing tissue repair Dense irregular connective tissue ○ These fibers are thicker, interwoven, and more randomly distributed than fibers of dense regular ○ The irregularly placed fibers allow the tissue to sustain tension exerted from many different directions ■ Located in the dermis (deep skin layer) ○ Found in the attachment between bones of the spinal columns ■ Portions of the heart Cartilage ○ A rigid connective tissue that provides support, frameworks, and attachments; protects underlying tissues; forms structured models for many developing bones ○ Chondrocytes: cartilage cells that occupy small changers called lacunae and lie completely within the extracellular matrix ○ A cartilaginous structure is enclosed in a covering of connective tissue called perichondrium ○ Hyaline cartilage: the most common type of cartilage; has very fine collagen fibers in its extracellular matrix and kind of looks like glass

Found in joint, soft part of nose, and supporting rings of the respiratory passages Elastic cartilage: more flexible because its extracellular matrix has a dense network of elastic fibers; provides framework for external ears and larynx Fibrocartilage: very tough tissue; a shock absorber for structures; forms pads (intervertebral discs) between vertebrae of the spinal column ■

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Most rigid connective tissue Hardness is largely due to mineral salts, such as calcium phosphate and calcium carbonate, between cells This extracellular mix also contains abundant collagen fibers, which are flexible and reinforce the mineral components of bone Also contains red marrow, which forms blood cells Osteoblasts: deposit bony matrix in thin layers called lamellae, which form concentric patterns around longitudinal tubes called central, or Haversian, canals which contain capillaries Once osteoblasts are in lacuna surrounded by matrix, they are osteocytes Osteon: a cylinder shaped unit, also known as a Haversian system The bone cells have many cytoplasmic processes that extend outward and pass through tiny tubes in the extracellular matrix called canaliculi

Blood ○ Composed of cells suspended in a fluid extracellular matrix called plasma ○ These cells include red blood cells, white blood cells, and cellular fragments called platelets ○ Red blood cells transport gases, white blood cells fight infection, and platelets are involved with blood clotting ○ Most blood cells form in special tissues (hematopoietic tissues) in red marrow within the hollow parts of certain parts ○ Red blood cells are the only type of blood cells that function entirely in blood vessels ○ White blood cells typically migrate from the blood through capillary walls to connective tissues

Types of Membranes: ● Membranes: sheets of cells ● Epithelial membranes: thin structures that are composed by epithelium and underlying connective tissue ● Three major types of epithelium membranes serous, mucous, and cutaneous ● Serous membranes: line the body cavities that do not open the outside and reduce friction between the organs and cavity walls ○ Forms the inner linings of the thorax and abdomen, and they cover the organs in these ○ Consists of a layer of simple squamous epithelium (mesothelium) and a thin layer of areolar connective tissue

Cells of serous membrane secrete watery serous fluid, which helps lubricate membrane surfaces Mucous membranes: line the cavities and tubes that open to the outside of the body ○ These include the oral and nasal cavities and the tubes of digestive, respiratory, urinary, and reproductive systems ○ Goblet cells within a mucous membrane secrete mucus Cutaneous membrane: composed entirely of connective tissue; lines joints ○

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Muscle Tissues: ● Are contractive; they can shorten and thicken ● As they contract, muscle cells pull at their attached ends, which moves body parts ● The cells that comprise muscle tissue are also called muscle fibers because they are elongated ● Approximately 40% by weight of the body is skeletal muscle, and almost 10% is smooth and cardiac muscle combined ● Three types of muscle tissue are skeletal, smooth, and cardiac Skeletal Muscle Tissue ● Forms muscle that typically attach to bones and can be controlled by conscious effort ● It is also called voluntary muscle tissue for that reason ● Skeletal muscle cells have alternating light and dark cross-markings called striations ● Each cell has many nuclei (multinucleate) ● Must be stimulated by a nerve cell to contract...