Epithelium and Connective Tissue Lecture Notes PDF

Types of Tissues (epithelial tissue) Prof. Dr. Marwa G.A. Hegazy  L.O. (Lecture 2) Objective 2 – The student will be able to: Identify four primary types of tissues in human body (epithelial, connective, muscle, nervous)and describe their primary function. Identify types...

Types of Tissues (epithelial tissue) Prof. Dr. Marwa G.A. Hegazy  L.O. (Lecture 2) Objective 2 – The student will be able to: Identify four primary types of tissues in human body (epithelial, connective, muscle, nervous)and describe their primary function. Identify types of epithelium (simple, stratified). Discuss different types of connective tissue (loose, dense, adipose, cartilage, bone, blood)and describe their characteristics and functions.  Group of cells of the same type form a larger structure called a tissue (e.g. – skin, muscle). Multiple tissues can form an organ (e.g. – eye, kidney). This variation among cell groups is known as differentiation.  Types of Tissues 1)Epithelium (covering) 2)Connective (support) 3)Muscle (movement) 4)Nervous (control) Types of tissues Characteristics (Traits): Sheets of cells closely attached to each other forming a protective barrier. Specialized contacts/cell junctions Polarity : o Always has one free (apical) surface open to outside the body or inside (cavity) an internal organ. o Always had one fixed (basal) section attached to underlying connective tissue. Avascularity: o Has no blood vessels but can soak up nutrients from blood vessels in connective tissue underneath. Innervated : o Can have lots of nerves in it. Very good at regenerating (fixing itself). i.e. sunburn, skinned knee. E.g. skin, lining of gut, mucous membranes  Function of Epithelial Tissue Protection  Skin protects from sunlight & bacteria & physical damage. Absorption  Lining of small intestine, absorbing nutrients into blood Filtration  Lining of Kidney tubules filtering wastes from blood plasma Secretion  Form Different glands, produce, oil, digestive enzymes and mucus  Classification of epithelia According to thickness – “simple” - one cell layer – “stratified” – more than one layer of cells (which are named according to the shape of the cells in the apical layer) According to shape – “squamous” – wider than tall – “cuboidal” – as tall as wide – “columnar” - taller than wide  (Absorption and filtration) Protection where diffusion is important where tissues are involved in secretion and absorption: larger cells because of the machinery of production, packaging, and energy requirements  Features of Apical Surface of Epithelium  Microvilli: (ex) in small intestine  Finger-like extensions of the plasma membrane of apical epithelial cell Increase surface area for absorption  Cilia: (ex) respiratory tubes Whip-like, motile extensions Moves mucus, etc. over epithelial surface 1-way  Flagella: (ex) spermatoza Extra long cilia Moves cell  Features of the Basal Surface of Epithelium Basal lamina: supportive sheet between epithelium and underlying connective tissue – Selective filter Basement membrane = basal lamina plus underlying reticular fiber layer – Attaches epithelium to connective tissue below Sometimes the two are used interchangeably  Features of Lateral Surface of Epithelium Cells are connected to neighboring cells via: – Proteins-link cells together, interdigitate – Contour of cells-wavy contour fits together – Cell Junctions Desmosomes Tight Junctions Gap junction  JUNCTIONS Anchoring Junctions (adherens junctions) and desmosomes): o Provides adhesion of one cell to its neighbors, cell-to-cell adherence Occluding Junctions (tight junctions): o joins cells together; seals to prevent loss of material (impermeable barrier to fluid). Communicating Junction (Gap Junctions) o connects the cytoplasm of two cells, which allows various molecules and ions to pass freely between cells  Pop Quiz Name the Epithelial Feature! 3 Cilia 3 1 2 Tight 1 junction Microvilli 2 Basement 4 membrane 4  Simple Squamous Epithelium Structure Single Layer of flattened cells Disc shape central nuclei Function Absorption, and filtration Not effective protection – single layer of cells. Location Walls of capillaries, air sacs in lungs Form serous membranes in body cavity  Simple Cuboidal Epithelium Structure Single layer of cube shaped cells Large spherical central nuclei Function Secretion and transportation in glands, filtration in kidneys Location ducts (pancreas & salivary), kidney tubules, covers ovaries  Simple Columnar Epithelium Structure Elongated layer of cells with round or oval nuclei at same level Function Absorption, Protection & Secretion When open to body cavities – called mucous membranes Special Features Microvilli, bumpy extension of apical surface, increase surface area and absorption rate. Goblet cells, single cell glands, produce protective mucus. Location Linings of entire digestive tract, fallopian tubes, uterus (ciliated)  Pseudostratified Epithelium Structure Cilia Irregularly shaped cells with nuclei at different levels – appear stratified, but aren’t. Some of cell not reaching the surface Function Absorption and Secretion Goblet cells produce mucus Cilia (larger than microvilli) sweep mucus Location Basement Respiratory Linings & Reproductive Membrane tract  Stratified Squamous Epithelium Structure Many layers, stronger than simple Basal cell is cuboidal or columnar and surface cell are squamous (flattened) Function Protection Keratin (Superficial cells gradually die &form keratin) (protein) is accumulated in older cells near the surface – waterproofs and toughens skin. Location Skin (keratinized), dry exposed surfaces Vagina, Oral cavity, Esophagus , Cornea (Non keratinized) wet exposed surfaces  Stratified cuboidal Generally 2 layers of cube like cell protection Male urethra Sweat glands Stratified Cuboidal (layers of cuboidal only)  Stratified columnar Several cell layers Basal cell cuboidal, superficial cell elongated and columnar The cells function in secretion and protection Epiglottis Conjunctiva of the eye Pharynx Anal mucous membrane  Simple cuboidal Pop E Quiz!! Can You Identify the columner epithelium Classes of Epithelium? D Simple squamous Pseudostratified columnar A B Stratified Squamous Epithelium C Connective Tissue Without it you’d fall apart.  It contains sparsely packed cells scattered throughout an extracellular matrix  The matrix consists of fibers in a liquid, jellylike, or solid foundation  Connective tissue function:  Binding and support  Protection  Insulation  Transportation  Connective tissues characteristics: › Mesenchyme as their common tissue of origin (embryonic tissue; mesoderm). › Varying degrees of vascularity and most also have nervous innervation › Nonliving extracellular matrix, consisting of ground substance and fibers proteins Connective Tissue Consists of three basic elements: Cells, fibers and Extra-cellular matrix  C.T. Components Cells Fibers Matrix Soft---C.T. proper Rubbery--Cartilage Solid---Bone Fluid---Blood  CELLS  Fixed: resident population of cells that have developed and remain in place within the CT, they are stable and long- lived.  Fibroblasts  Adipose cells  Pericytes  Mast cells  Macrophages  Transient: free or wandering, originate in the BM and circulates in the blood stream  Plasma cells  Lymphocytes  Neutrophils  Eosinophils  Basophils  Monocytes  Macrophages  Matrix Cells Cells in connective tissue make and maintain the ground substance and fibers. Each type of conn. Tissue have immature and mature forms of these cells. Immature cells have suffix “-blast” – actively produce matrix (Active state). Mature cells have suffix “-cyte” – maintain health of matrix, reverting to blasts to regenerate matrix after injury. – Fibroblasts – make conn. Tissue/fibers – Chondroblasts – make cartilage, – Osteoblasts – make bone – Hematopoeitic stem cells – make blood  Matrix Fibers Fibers are embedded in ground substance to add strength/flexibility 1.Collagen Fibers: Large fibers made of the protein collagen and are typically the most abundant fibers. Promote tissue flexibility. They are tough and provides high tensile strength. 2.Elastic Fibers: Intermediate fibers made of the protein elastin. Branching fibers that allow for stretch and recoil. 3.Reticular Fibers: Small delicate, branched fibers that have same chemical composition of collagen. Forms structural framework for organs i.e. join connective CLASSIFICATION OF CONNECTIVE TISSUE 1. True Connective Tissue/CTP a. Loose Connective Tissue b. Dense Connective Tissue 2. Supportive Connective Tissue a. Cartilage b. Bone 3. Liquid Connective Tissue a. Blood  CLASSIFICATION OF CONNECTIVE TISSUE 1. True Connective Tissue/CTP a. Loose Connective Tissue b. Dense Connective Tissue 2. Specialized Connective Tissue a. Cartilage b. Bone c. Blood Connective Tissue  Loose (Areolar) C.T Reticular C.T Most common type Cells All types of cells Reticular cells All types of fibers (collagen) Fine network of Fibe More abundant matrix reticular fibers. rs Moderate amount Matr ix  Potential cavities which can  Delicate type accommodate large amount of fluids and gases.  Flexible and well-vascularized  Everywhere in the body  Supportive frame except the brain: work in stroma of Sites  Spaces between the organs. organs : spleen &lymph node & liver  Exchanging of nutrients to  Supportive Func and from blood vessels tion  Binding of structures  Adipose C.T Structure Mainly fat cells Cell Fine network of. Collagen and elastic fibers. Fibers White adipose C.T Brown adipose C.T  Fat cells are unilocular  Fat cells are multilocular  Less vascularity  High vascularity  Affected by diet and hormones  Affected by hormones only.  Under the skin (subcutaneous  New born replaced gradually by layer ) the white type Sites  Around kidney &other organs  Heat insulation.  Thermogenesis in newborn  Storage of fat &giving the skin Function contour  Support organs  White fibrous C.T Structure Cell Fibroblasts Fibers Collagen fibers packed into bundles. Matrix Minimal amount (more vascularity). Character -Very dense type (white in fresh section). s -Resistant and less flexible. Regular Irregular Regularly arranged irregularly arranged collagen collagen bundles with bundles with scattered rows of fibroblasts in fibroblasts between Sites Tendons &Cornea Ligaments & Sclera of eye Capsule of organs -Withstand stretch in one -Withstand stretch in all Function directions directions  Yellow elastic C.T Structure Cell Fibroblasts Fibers Regular parallel elastic fibers. Matrix Small amount. -Dense type (yellow in fresh section). -Great elastic power. Characters  Aorta and large arteries  Trachea Sites  Some ligaments -Great elastic power Function Connective Tissue: Hyaline Cartilage Figure 4.8g  Connective Tissue: Fibrocartilage Cartilage Matrix similar to hyaline cartilage but less firm with thick collagen fibers Provides tensile strength and absorbs compression shock Found in intervertebral discs, the pubic symphysis, and in discs of the knee joint Figure 4.8i  Connective Tissue: Elastic Cartilage Similar to hyaline cartilage but with more elastic fibers Maintains shape and structure while allowing flexibility Supports external ear (pinna) and the epiglottis Figure 4.8h Connective Tissue: Bone (Osseous Tissue) Figure 4.8j Connective Tissue: Blood Figure 4.8k  Connective Tissue Collagenous fiber Loose Chondrocytes connective Cartilage tissue 120 µm 100 µm Elastic fiber Chondroitin sulfate Nuclei Fat droplets Fibrous connective Adipose tissue tissue 150 µm 30 µm Osteon White blood cells Bone Blood 55 µm 700 µm Central canal Plasma Red blood cells  Mescher AL (2018): Junqueira’s basic Histology Text and Atlas 14th edition  NEXT Lymphatic System