Biology Chapter 3 Part 2 Tissues PDF

Biology Fall 2024/2025 Chapter 3 Cells & Tissues Part 2  Body Tissues Introduction Tissue: group of cells that are similar in structure and function Four Primary types: Epithelial tissue (epithelium) Connective tissue Nervous tissue Muscle tissue ...

Biology Fall 2024/2025 Chapter 3 Cells & Tissues Part 2  Body Tissues Introduction Tissue: group of cells that are similar in structure and function Four Primary types: Epithelial tissue (epithelium) Connective tissue Nervous tissue Muscle tissue  Nervous tissue: Internal communication Brain, spinal cord, and nerves Muscle tissue: Contracts to cause movement Muscles attached to bones (skeletal) Muscles of heart (cardiac) Muscles of walls of hollow organs (smooth) Epithelial tissue: Forms boundaries between different environments, protects, secretes, absorbs, filters Lining of GI tract organs and other hollow organs Skin surface (epidermis) Connective tissue: Supports, protects, binds other tissues together Bones Tendons Fat and other soft padding tissue Figure 3.22 Summary of the major functions and body locations of the four tissue types: epithelial, connective, muscle, and nervous tissues.  Epithelial Tissue Location: Covers all free body surfaces and contain versatile type of cells. Body linings (body cavities, GI tract, absorptive organs) Body covering (outer layer of skin) Glandular tissues (hollow organs and excretory tissues or glands) Functions Protection (skin outer layer, epithelial lining of respiratory tract; cilia), absorption (digestive system), filtration (kidney), secretion (glands) Figure 3.17a Classification and functions of epithelia. Apical surface Epithelium Characteristics Cells fit closely together Basal Simple and often form sheets surface Rich in tight junctions and desmosomes except for glandular tissue Apical surface The apical surface is the free surface of the tissue The lower surface of the epithelium rests on a basement membrane Basal Avascular (no blood supply) surface Stratified Regenerate easily if well nourished Figure 3.17a Classification and functions of epithelia. Apical surface Basal Simple surface Classification of Epithelia Apical surface Number of cell layers Simple—one layer Stratified—more than one layer Basal surface Stratified (a) Classification based on number of cell layers Figure 3.17b Classification and functions of epithelia. Squamous Classification of Epithelia Cuboidal Shape of cells Squamous: Flattened, like fish scales Cuboidal: Cube-shaped, like dice Columnar: Column-like Columnar (b) Classification based on cell shape  Function of epithelial tissue related to tissue type Number of layers One layer: simple epithelial More than one layer: stratified Cell shape tissues epithelial tissues Squamous Diffusion and filtration Protection Secretion in serous membranes Cuboidal Secretion and absorption; ciliated Protection; these tissue types are rare types propel mucus or in humans reproductive cells Columnar Secretion and absorption; ciliated types propel mucus or reproductive cells Transitional Protection; stretching to accommodate distension of urinary structures  Simple Epithelia Simple squamous – Single layer of flat cells – Location; usually forms membranes Lines air sacs of the lungs Forms walls of capillaries Forms serous membranes (serosae) that line and cover organs in ventral cavity – Functions in diffusion, filtration, or secretion in membranes © 2015 Pearson Education, Limited.  Simple Epithelia Air sacs of lungs Nucleus of Nuclei of squamous squamous epithelial cell epithelial cells Basement membrane Photomicrograph: Simple squamous epithelium forming part Simple squamous of the alveolar (air sac) walls (275×). Figure 3.18a Types of epithelia and their common locations in the body.  Simple Epithelia Simple cuboidal: Single layer of cube-like cells Locations: Common in glands and their ducts Forms walls of kidney tubules Covers the surface of ovaries Functions in secretion and absorption; ciliated types propel mucus or reproductive cells Simple Nucleus of cuboidal simple epithelial cuboidal cells epithelial cell Basement membrane Basement membrane Connective tissue Photomicrograph: Simple cuboidal Simple cuboidal epithelium in kidney tubules (250×).  Simple columnar (Single layer of tall cells) Lines digestive tract from stomach to anus Mucous membranes (mucosae) line body cavities opening to the exterior Functions in secretion and absorption; ciliated types propel mucus or reproductive cells *Goblet cells are specific type of columnar cells that secrete mucus Nucleus of Mucus of a simple columnar goblet cell epithelial cell Simple columnar epithelial cells Basement Basement membrane membrane Photomicrograph: Simple columnar (c) Diagram: Simple columnar epithelium of the small intestine (575×).  Pseudostratified columnar All cells rest on a basement membrane Single layer, but some cells are shorter than others giving a false (pseudo) impression of stratification Location: Respiratory tract, where it is ciliated and known as pseudostratified ciliated columnar epithelium Functions in absorption or secretion Pseudo- Cilia stratified Pseudo- epithelial stratified layer epithelial layer Basement Basement membrane membrane Connective tissue Photomicrograph: Pseudostratified (d) Diagram: Pseudostratified ciliated columnar epithelium lining the (ciliated) columnar human trachea (560×).  Stratified Epithelia Stratified Squamous – Named for cells present at the free (apical) surface, which are flattened – Functions as a protective covering where friction is common – Locations—lining of the: Skin (outer portion) Mouth Esophagus © 2015 Pearson Education, Limited.  Nuclei Stratified squamous Stratified epithelium squamous epithelium Basement Basement membrane membrane Photomicrograph: Connective (e) Diagram: Stratified squamous Stratified squamous tissue epithelium lining of the esophagus (140×). Figure 3.18e Types of epithelia and their common locations in the body.  Stratified Epithelia Stratified cuboidal—two layers of cuboidal cells; functions in protection Stratified columnar—surface cells are columnar, and cells underneath vary in size and shape; functions in protection Stratified cuboidal and columnar – Rare in human body – Found mainly in ducts of large glands © 2015 Pearson Education, Limited.  Stratified Epithelia Transitional epithelium – Composed of modified stratified squamous epithelium – Shape of cells depends upon the amount of stretching – Functions in stretching and the ability to return to normal shape – Locations: urinary system organs © 2015 Pearson Education, Limited.  Basement membrane Transi- tional epithelium Transitional Basement epithelium membrane Connective tissue Photomicrograph: Transitional epithelium lining of (f) Diagram: Transitional the bladder, relaxed state (270×); surface rounded cells flatten and elongate when the bladder fills with urine. Figure 3.18f Types of epithelia and their common locations in the body. Simple and Stratified Epithelia  Glandular Epithelium Gland: – One or more cells responsible for secreting a particular product – Secretions contain protein molecules in an aqueous (water-based) fluid – Secretion is an active process Glands are of two major types: – Endocrine: ductless, their secretions (hormones) diffuse into bloodstream to reach target cells; examples include thyroid, adrenal, pituitary – Exocrine: secretions empty through ducts into an epithelial surface; examples include sweat gland and oil glands, liver, pancreas  Connective tissue General characteristics: Most abundant type of tissues Mostly well-vascularized (bone); some poorly vascularized (tendons and ligaments) or avascular (cartilage) Connective tissue is made of cells and nonliving substances that covers the outside of the cells. This nonliving substance is called the extracellular matrix  Connective tissue (cont.) The extracellular matrix is made by the cells of the connective tissue itself and consists of 2 main elements: – Ground substance: water + proteins + polysaccharides and minerals. The protein form a gluey substance causing cells to adhere to the matrix fibers. – Fibers of various types: white collagen fibers (high tension strength), yellow elastic fibers (stretch and recoil), and reticular fibers (form organ frameworks). Extracellular matrix enables connective tissue to form soft packing around organs for protection, to bear weight, and withstand stretching and abrasion. Types of connective tissue: bone, cartilage, dense connective tissue, loose connective tissue, and blood 1. Bone (osseuos): Osteocytes (bone cells) sitting in cavities called lacunae (pits). Lacunae are surrounded by hard extracellular matrix made of Ca++ salts & many collagen fibers 2. Cartilage: chondrocytes (cartilage cells) sitting in lacunae Hyaline cartilage: most abundant type, rich in collagen fibers; present in larynx, voice box, between ribs & breastbones; skeleton of the fetus starts as hyaline cartilage before becoming bone but growth plates in long bones remain cartilagenous. Fibrocartilage: highly compressible & forms the cushioning discs between vertebrae Elastic cartilage: found in elastic structures (e.g. external parts of ears) 3. Dense Connective Tissue Also called dense fibrous tissue Rich in collagen fibers + fibroblasts that manufacture the building blocks of collagen fibers Forms strong ropelike tendons and ligaments Tendons connect muscle to bone Ligaments connect bone to bone at joints The dense connective tissues also makes up the dermis (middle layers) of the skin 4. Loose connective tissue Softer than dense connective tissue and has fewer fibers and more cells (fibroblasts) 3 different types: a. Areolar tissue [small open space]: The most widely distributed connective tissue; soft, sticky & pliable (flexible), able to cushion & protect It wraps and glues body organs together; e.g., lamina propria is a Layer of areolar tissue underlies all membranes. Spaces in areolar tissue function as reservoirs for water & salts (interstitial fluid). Inflammation causes areolar tissue to take up the excess water and become puffy (edema). 4. Loose connective tissue (cont.) b. Adipose tissue: fat storing cells (adipocytes). The fat vacuole is so big that it displaces the nucleus and occupies most of the cytoplasm. It is called signet ring cells. Adipose tissue found beneath skin (insulation), kidneys (protection), hips and breast (fuel storage) c. Reticular tissue: a delicate network of reticular fibers and reticular cells (similar to fibroblasts) that form the stroma (matt or internal framework) of lymphoid organs  Helps to give organs like spleen, lymph nodes, and bone marrow their architecture  5. Blood Considered connective tissue as it contains blood cells that originate from bone marrow and it is surrounded by a matrix, the plasma. Consists of a liquid matrix (plasma) which accounts for up to 55% of blood volume + cellular components that account for about 45% of blood volume. Cellular part consists of red blood cells (carry oxygen to tissues), white blood cells (immune function), and platelets (homeostasis and prevention of excessive blood loss)  Muscular tissue Classified into 3 types based on function and related features Skeletal Muscle: Attached to skeleton (bones): by contracting/relaxing can move bones (provide for mobility of organism) Cells are long, cylindrical, multinucleated, and have striations (stripes) Muscle cells are elongated to provide long axis of contraction. They are often called muscle fibers.  Cardiac (heart) muscle: Found only in heart, involuntary Uninucleated, Striated, and short but branched. Branching junctions are called intercalated discs The intercalated discs synchronize contraction & relaxation of heart muscle. They are rich in gap junctions for rapid exchange of ions Smooth (visceral) Muscles: Called smooth because no striations Involuntary Cells are uninucleated , spindle shaped Present in all hollow organs of body (stomach, uterus, blood vessels, etc.). It enables organs to change diameter. Peristalsis of digestive tract and uterus contraction are good examples.  Nervous tissue Cells of the nervous tissue are known as neurons. Neurons receive and conduct electrochemical impulses Neurons show a unique structure: axons and dendrites (neuron processes) Neuroglia: specialized cells that insulate, support and protect the delicate neurons of the nervous system