Lecture Notes - Chapter 4 PDF

**[Lecture Notes - Chapter 4]** **N. Marlo Ballard** **4-1 -- The Four Types of Tissue** - **Tissues** are collections of cells and cell products that perform specific, limited functions - Different types of tissues combine to form **organs**, such as the heart or liver...

**[Lecture Notes - Chapter 4]** **N. Marlo Ballard** **4-1 -- The Four Types of Tissue** - **Tissues** are collections of cells and cell products that perform specific, limited functions - Different types of tissues combine to form **organs**, such as the heart or liver - **Histology** is the study of tissues - Four main types of tissues: 1. **Epithelial** **tissue -- covers exposed surfaces, lines passageways, forms glands** 2. **Connective** **tissue -- fills internal spaces, supports, transports, stores energy** 3. **Muscle** **tissue -- contracts to produce movement** 4. **Neural** **tissue -- carries information in the form of electrical signals** **4-2 -- Characteristics and Functions of Epithelial Tissue** 1. [Layers] of epithelial cells on top of a basement membrane called **epithelia** - Covers internal or external surfaces 2. [Collections] or clusters of epithelial cells forming **glands** - Produce fluid secretions or hormones 1. *Provide* *Physical* *Protection* - *Forms barriers that **protect** deeper tissues from mechanical or chemical damage* 2. *Controls* *Permeability* - Controls **permeability** by limiting substances that can move through the epithelium 3. *Produces* *Specialized* *Secretions* - Secretions provide **protection** and **communication** (chemical messengers) - Secretions are moved over the epithelium to provide **protection** & **lubrication** 4. *Provide* *Sensation* - *Contain sensory nerves* 1. **Polarity** -- epithelial cells have *apical* and *basal* surfaces A. **Apical surface -- this is the "free" (unattached surface)** - Secretions are put onto the apical surface of an epithelia - May have modifications - *Microvilli* increase absorption or secretion - *Cilia* (**ciliated** **epithelium**) move fluid B. **Basolateral surfaces** - **Lateral surface** -- Attachment along the "sides" of the cell to neighboring epithelial cells - **Basal surface** -- Attachment along the "bottom" of the epithelial cells to deeper cells or tissues at the **basement membrane (has two layers):** i. **Basal lamina** - Adjacent to and secreted by the epithelia - Clear, thin layer that acts as a filter ii. **Reticular lamina** - Adjacent to and secreted by the deeper connective tissues - Dense layer with thick fibers that provides strength and filtration 2. **Cellularity** -- epithelial tissues are composed almost entirely of cells that are tightly attached to one another. There is almost no space or material between epithelial cells. 3. **Attachment** -- epithelial cells are attached to other epithelial cells and to the ***basement** **membrane*** - Types of connections: A. **CAMs** (**cell adhesion molecules**) -Transmembrane proteins that function to connect large areas of plasma membrane B. **Cell junctions -** Specialized areas of the plasma membrane that form specific and localized connections i. **Gap** **Junctions** - Are held together by channel proteins called *connexons* - Forms an opening between cells - Permit the free diffusion of ions & small molecules between two cells - Allows for rapid communication between cells - Important for the coordinated contractions of the heart ii. **Tight** **Junctions** - Located on the lateral surface (but near the apical end of the cells) - Consists of the plasma membranes of two adjacent cells tightly bound together by interlocking membrane proteins - Prevents fluids and solutes from passing between cells - Isolates enzymes, acids, and wastes to the [lumen] of a passageway - Deep to the tight junction, an **adhesion belt forms a band that encircles the cell and binds it to neighboring cells** iii. **Desmosomes** - Strong, durable connections, like a "spot weld" - Help cells endure the mechanical stress (movement) - Two types: a. ***Spot* *desmosomes*** *-- t*ie adjacent cells together along the lateral surfaces b. ***Hemidesmosomes** - a*ttach cells to the basement membrane 4. **Avascularity** -- all epithelia lack blood vessels - **They obtain oxygen, nutrients, and get rid of wastes via the adjacent connective tissue** 5. **Regeneration** -- epithelial cells are continually being replaced for the maintenance and repair of epithelial tissue - Epithelial cells need to be replaced at a high rate due to: - exposure to enzymes, toxins, bacteria - mechanical abrasion - Cells are replaced by the division (mitosis) of **germinative** **cells** (stem cells) located next to the basement membrane **4-3 -- Classification of Epithelial Tissue** - Singular = **Epithelium**; Plural = **Epithelia** - Epithelia are classified by: A. The [shape] of the cells - **Squamous** - thin and flat - **Cuboidal** -- cube shape - **Columnar** - tall and slender, column-shaped B. The [number of layers] formed - **Simple** -- 1 layer of cells - Simple epithelia often have the following functions of [secretion] and [absorption] - **Stratified** - 2 or more layers of cells - **Stratified epithelia often have the function of [protection]** - Types of epithelia: 1. [Squamous epithelium] A. **Simple squamous epithelium** -- diffusion, control of permeability, secretion and reduction of friction - **Types of simple squamous epithelium** - **Mesothelium** -- lines body cavities - **Endothelium** -- lines the interior of the heart and blood vessels B. **Stratified squamous epithelium** -- protection from mechanical forces and abrasion - **Keratinized** - impregnated with keratin protein for strength and water resistance - forms the outer layer of skin - **Non-keratinized** - Lines the inside of the mouth, esophagus, and vagina 1. [Cuboidal epithelium] A. **Simple cuboidal epithelium** - secretion & absorption - Found in glands, ducts, and parts of the kidney B. **Stratified cuboidal epithelium** -- protection, secretion & absorption - Relatively rare tissue found in the ducts of mammary and sweat glands 2. [Columnar epithelium] A. **Simple columnar epithelium** -- secretion & absorption - Found in the stomach, small intestine, and large intestine B. **Stratified columnar epithelium** -- protection - Relatively rare tissue found in the pharynx, urethra, and anus C. **Pseudostratified columnar epithelium** -- secretion - Typically have [cilia] to move secretions - Looks stratified but is really just one layer - All cells contact the basement membrane - Found in the nasal cavity, trachea, and bronchi 3. [Transitional epithelium] -- allows for stretching and recoiling - Returns to its previous shape without damage - Appearance changes as stretching occurs - Situated in regions of the urinary *system (e.g., ureters & urinary bladder)* **[GLANDULAR EPITHELIA]** - **Glands** are collections of epithelial cells that produce secretions 1. **Exocrine** **glands** - *Secretions are discharged* into **ducts** and delivered to epithelial surfaces 2. **Endocrine** **glands** - No ducts; release *hormones* that enter the blood - [Types of Exocrine Glands:] - Classification according to The **STRUCTURE** of the Gland: 1. **Unicellular glands** - Secrete *mucin*, which mixes with water to form **mucus** - **Mucous** **cells** are found scattered along the pseudostratified ciliated columnar epithelium of the respiratory tract - **Goblet cells are found scattered along the simple columnar epithelium of the digestive tract** 2. **Multicellular glands** - *[Structure] of the duct* - ***Simple*** -- single duct - ***Compound*** -- multiple ducts merge on their way from the gland - *[Shape] of secretory portion of the gland* - ***Tubular*** (tube shaped) -- may be straight or coiled - ***Alveolar*** or ***acinar*** (blind pockets) - Classification according to The **TYPE OF SECRETION** the Gland Produces: 1. ***Serous* *glands*** - Produce thin, watery secretions containing enzymes 2. ***Mucous* *glands*** - Secrete mucins which form thick mucus secretions 3. ***Mixed* *exocrine* *glands*** - Contain both serous and mucous gland cells and therefore produce a secretion that is intermediate in viscosity - [Modes of glandular secretion] (how the gland cells release their secretion) 1. **Merocrine** **Secretion** - Product released by the exocytosis of secretory vesicles - Does not damage the cell - *For example, sweat glands* 2. **Apocrine** **Secretion** - Product released by the shedding of cytoplasm at the apical surface - Cell is damaged and will have to regenerate - *For example, mammary glands* 3. **Holocrine** **Secretion** - Released by cells bursting - Kills the gland cells - Gland cells replaced by stem cells - *For example, sebaceous glands* **4-4 -- Characteristics and Functions of Connective Tissue** 1. **specialized cells** 2. **extracellular matrix** - makes up the majority of the tissue volume - determines the specialized function of the CT - consists of: - Solid [extracellular] **protein fibers** - Fluid/gel/solid [extracellular] **ground** **substance** 1. Establishing a structural framework for the body, providing strength & stability 2. Supporting, surrounding, and interconnecting other types of tissue 3. *Protect and maintain positions of internal organs* 4. Provide routes for blood vessels, lymphatic vessels, and nerves 5. Transport fluids and dissolved materials 6. Defending the body from invading microorganisms 7. Storing energy reserves A. - Found in all categories of connective tissue proper - Secrete the ground substance and protein fibers of the matrix B. - Maintain the fibers of connective tissue proper C. - Each cell stores a single, large fat droplet D. - Have the ability to differentiate into other types of CT cells E. F. G. - Phagocytose pathogens and damaged cells - *Fixed* *macrophages* stay in tissue; *free* *macrophages* migrate in & out I. - Respond to signals from other cells *(ie. macrophages and mast cells)* - *Examples include neutrophils and eosinophils* H. - *Play a role in defense; produce antibodies* 1. 2. **Collagen fibers** - Most common type of fiber in connective tissue proper - The structural unit of collagen fibers is **collagen protein** - **Collagen protein is the most abundant protein in the body** - Thick, long, straight, and unbranched - Strong and flexible, but [not] elastic (stretchy) - Resist force in [one] direction - *Found in most connective tissues but especially the skin, tendons, and ligaments* 3. **Reticular fibers** - Form a network of interwoven fibers (stroma) that stabilize cells and structures - Like collagen fibers, the structural unit is also **collagen protein** - Thin and branching - Strong and flexible but not elastic - Resist forces in [many] directions - *Found in organs such as the kidney, liver, and spleen, and in sheaths around organs* 4. **Elastic fibers** - Found in tissues that need to stretch - Return to original length after stretching - Contain ***elastin protein*** - Branched and wavy - *Found in the elastic ligaments of vertebrae, and elastic arteries such as the aorta* - Is clear, colorless, and viscous - Viscosity (thickness) comes from the presence of proteoglycans and glycoproteins - Fills spaces between the cells and fibers - Slows pathogen movement 1. **Connective tissue proper -** Connects and protects A. **Loose Connective Tissue Proper** - More ground substance, fewer fibers - *For example, fat* (*adipose* *tissue*) B. **Dense Connective Tissue Proper** - Less ground substance, more fibers - *For example, tendons and ligaments* 2. **Fluid connective tissues -- For t**ransport - *Examples are blood & lymph* 3. **Supporting connective tissues -- For s**tructural strength - *Examples are cartilage & bone* **4-5 -- Connective Tissue Proper and the Fasciae** 1. **Embryonic Connective Tissue** - Is not found in adults A. **Mesenchyme** = embryonic connective tissue - The first connective tissue *found in the embryo* - Don't confuse mesenchyme tissue with mesenchyme cells - Mesenchyme [tissues] are only found in the embryo - Mesenchyme [cells] are stem cells found in adults B. **Mucous** **connective** **tissue** (Wharton's Jelly) - Loose embryonic connective tissue *found in the umbilical cord* 2. **Loose Connective Tissue Proper** - "Packing materials" - fills spaces between organs, cushion cells, and supports attached epithelia - Three types in adults: 1. **Areolar CT** - Least specialized type of CT - May contain any cell type found in CT proper - Matrix is an open framework and contains: - Viscous ground substance - Collagen & elastic fibers - Blood vessels and capillary beds - *Found in the deep layer of the skin and many other places* 2. **Adipose CT** - Contains many **adipocytes** (fat cells) - Shrink as fats are released -- as you lose weight - Expand to store triglycerides (fat) -- as you gain weight - Adipocytes don't divide, but new adipocytes may be created from mesenchyme cells - Two types of adipose tissue: A. **White** **fat -** Most common type of fat, found in adults - Stores triglycerides for energy - Absorbs shocks and slows heat loss (insulation) B. **Brown** **fat -** Found in infants and young children - It is brown because it is more vascularized than white fat - Adipocytes have many mitochondria - When stimulated the fat is broken down and released as heat energy which is absorbed by surrounding tissues - Important for body temperature homeostasis in infants 3. **Reticular CT** - Complex, three-dimensional network - Consists of fibers (**stroma**) that support functional cells (**parenchyma**) - *Found in reticular organs: spleen, liver, lymph nodes, and bone marrow* 3. **Dense Connective Tissue Proper** - Dense with collagen fibers, but also contains elastic fibers - Three types: 1. **Dense Regular CT** - Contains fibroblasts and tightly packed collagen fibers in parallel to resist force in one direction - Blood vessels are not plentiful - Makes damaged tendons & ligaments slow to heal - *Found in tendons (connects muscle to bone) & ligaments (connects bone to bone)* 2. **Dense Irregular CT** - Interwoven networks of collagen and elastic fibers - Fibers are layered in different orientations to resist forces in different directions - *Found in* - *the deep layer of the skin* - *capsules surrounding certain organs (e.g., liver, kidneys, spleen)* - *membrane sheaths around bone and cartilage* 3. **Elastic CT** - Contains abundant amounts of elastic fibers - *Found in the* - *elastic ligaments of spinal vertebrae* - *walls of elastic arteries such as the aorta* - Three layers of fasciae 1. ​**Superficial** **fascia -- most superficial layer** - Made of adipose tissue and areolar CT - Separates skin from underlying tissues, allowing them to move independently - Provides padding 2. ​**Deep** **fascia -- middle layers of fascia** - Made of layers of dense regular connective tissue - The fibers in each layer are oriented in different direction to add strength and form a strong fibrous internal framework - Fibers connect to organ capsules, the membranes around bones and cartilage, and the connective tissues in muscles to form supportive interconnections 3. ​**Subserous** **fascia -- deepest layer of fascia** - Made of areolar CT - Separates the deep fascia from the mesothelium of serous membranes that line body cavities **4-6 -- Fluid Connective Tissues** 1. **Interstitial fluid** -- Fluid between cells - Formed when blood pressure forces fluid out of capillaries 2. **Plasma** of blood - Confined to blood vessels 3. **Lymph** - Confined to lymphatic vessels 1. **Blood consists of:** A. Watery matrix is called **plasma** B. Cells and cell fragments, collectively known as **formed elements** i. Red blood cells (erythrocytes) - carry oxygen to body tissues ii. White blood cells (leukocytes) -- immune defense iii. Platelets -- promote blood clotting 2. **Lymph** - Part of the lymphatic system and monitored by the immune system - Forms from **interstitial fluid** when it enters lymphatic capillaries - Eventually is returned to the venous system **4-7 - Supporting Connective Tissues** 1. **Cartilage** - Matrix is gel-like for shock absorption & protection - The gel-like quality comes from polysaccharide derivatives called **chondroitin sulfates which are found in the ground substance** - Cartilage cells, called **chondrocytes** live in chambers (spaces) called **lacunae** - Avascular because chondrocytes produce **antiangiogenesis factor** - This makes cartilage a poorly healing tissue - **Perichondrium** is the membrane that surrounds cartilage - Three types: A. **Hyaline cartilage** - Most common type of cartilage - Tough, somewhat flexible support - Reduces friction between bones - Matrix contains collagen fibers that cannot be seen under the light microscope - *Found in synovial joints, ribs, sternum, and trachea* B. **Elastic Cartilage** - Supportive but bends easily - Matrix contains abundant elastic fibers - *Found in external ear and epiglottis* C. **Fibrocartilage** - Very durable and tough - Matrix contains abundant collagen fibers - Limits movement - Resists compression and prevents bone-to-bone contact - *Menisci in knee joints, between pubic bones and intervertebral discs* 2. **Bone (osseous tissue)** - Strong -- for weight support - Calcified Matrix - made rigid by calcium salts of the ground substance - Resists shattering -- due to the presence of collagen fibers in the matrix - **Periosteum** is the membrane that surrounds bone - The **osteon** is the functional unit of compact bone - The **central canal** is at the center and contains blood vessels & nerves - The **lamellae** are layers of bone matrix around the central canal and contain: - spaces called **lacuna** contain **osteocytes** (bone cells) - channels called **canaliculi** - Allow substances (O~2~, CO~2~, nutrients, wastes) to diffuse between the central canal and osteocytes 8. **-- Membranes** - Consist of an epithelium supported by connective tissue 1. **Mucous membranes** (**mucosae**) -- lines body cavities that are open to the exterior of the body *(For example: digestive, respiratory, urinary, and reproductive tracts)* - Consists of a layer of epithelium on top of a layer of CT called the **lamina propria** - Mucous or another secretion is necessary to keep the epithelial surface moist - to reduce friction - to facilitate absorption and excretion 2. **Serous membranes (serosae)** -- lines body cavities that are not open to the exterior of the body *(For example: thoracic cavity and abdominal cavity)* - Consists of a layer of simple squamous epithelium on top of areolar CT (subserous fascia) - Thin yet strong - Produces **serous fluid** to reduce friction - Layers A. **Visceral layer** (**serosa**) -- covers the organs B. **Parietal layer** -- lines or forms the walls of the cavity - Locations - **Pleura** -- covers the [lungs] and lines the pleural cavities - **Pericardium** -- Covers the [heart] and lines the pericardial cavity - **Peritoneum** -- Covers [abdominal organs] & lines the peritoneal cavity 3. **Cutaneous membrane** -- [skin] is a membrane that is thick, water-resistant, and dry 4. **Synovial membranes** -- lines moving, articulating joint cavities - The only membrane that lacks a true epithelial component - Protects the ends of long bones - Joint movement stimulates the release of synovial fluid for lubrication **4-9 -- Muscle Tissue** - Elongated cells that are specialized to contract and produce movement - Three types of muscle tissue: 1. **Skeletal muscle** - Large body muscles that move the skeleton for body motion - Cells are very long, multinucleated, striated (banded appearance) - Voluntarily controlled 2. **Cardiac muscle** - Only found in the heart - Cells are branching, uninucleated, striated - Cells are connected and communicate at **intercalated discs** - Involuntary control 3. **Smooth muscle** - Found in the walls of hollow, contracting organs - *(blood vessels, urinary bladder; respiratory, digestive, and reproductive tracts)* - Cells are small and spindle-shaped, uninucleated, non-striated - Involuntary control **4-10 -- Nervous Tissue** - Concentrated in the brain, spinal cord, and nerves - Responsible for - Sensing the internal or external environment - Conducting signals through the body (electrical impulses) - Processing information and controlling responses - Two main types of cells in nervous tissue 1. **Neurons** - main functional cell, conducts signals; three main regions A. **Cell body** -- contains the nucleus and most other organelles B. **Dendrites** -- receives a signal C. **Axon** -- sends a signal 2. **Neuroglia** -- supporting cells, repairs and supplies nutrients to neurons **4-11 -- Tissue Response to Injury** 1. **Inflammation** (also called the inflammatory process) - Can be caused by A. Trauma (physical injury) B. Infection (the presence of harmful pathogens) - Initiation of the Inflammatory Process: A. Damaged cells release chemicals into the surrounding tissues B. Chemicals activate **mast cells**, which then release 3 factors: histamine, heparin, and prostaglandins - Causes the 4 cardinal signs of inflammation: - Blood vessels dilate which increases blood circulation to the area causing ***[warmth]*** and ***[redness]*** - Increased blood flow enhances oxygen delivery, allows for removal of toxins and waste - Brings phagocytes into the area - Increased permeability of capillary walls causes plasma to leak into the area causing ***[edema]*** (swelling) - Abnormal conditions and chemicals released cause ***[pain]*** C. Enzymes from lysosomes destroy injured cells and tissues, leading to tissue death called **necrosis** - If necrotic tissue and cell debris (**pus**) become trapped, then an **abscess** has formed D. Phagocytes eventually clean up the area 2. **Regeneration** - When the injury or infection is cleaned up, healing (regeneration) begins - The Process of Regeneration: A. Fibroblasts move into necrotic area and lay down collagen fibers to bind the area together (scar tissue) B. New cells migrate into area or are produced by mesenchymal stem cells - Not all tissues can regenerate - Epithelia, most connective tissues, and smooth muscle regenerates well - Cartilage, skeletal muscle, cardiac muscle and nervous tissues regenerate poorly, or not at all **4-12 -- Effect of Aging on Tissues** - Speed and efficiency of tissue repair decrease due to lower metabolism, hormonal changes, and reduced physical activity: - Thinning epithelia & connective tissues - Increased bruising, joint pain, & bone brittleness - Mental deterioration - Cardiovascular disease (\#1 cause of death in US) - Cancer rates increase with age - Twenty-five percent of all people in the United States develop cancer at some point - \#2 cause of death in the United States