Note Oct 17, 2024: Chapter 4: Tissues PDF

Chapter 4: Tissues Two fundamental kinds of cells in the body: 1.) Sex cells (gametes) ◦ Eggs ◦ Sperms Produced by cell division mechanism called: meiosis 2.) Somatic cells (soma = body): there are 200 different types of cells in the human body produced by: Mitosis (cell division) B...

Chapter 4: Tissues Two fundamental kinds of cells in the body: 1.) Sex cells (gametes) ◦ Eggs ◦ Sperms Produced by cell division mechanism called: meiosis 2.) Somatic cells (soma = body): there are 200 different types of cells in the human body produced by: Mitosis (cell division) Body Tissue cells of similar function and/or structure can be grouped together to form tissue There are four types of tissue that make up our bodies: ◦ Epithelial Tissue - forms the linings, covers, and glands = skin is a good example ◦ Connective tissue - connects and supports other tissues; transports materials and stores energy reserves = tissue underneath the skin ◦ Nervous tissue - specialized to convey electrical impulses: control ◦ Muscle tissue - specialized contractile tissue: movement, heart contraction, and muscular walls of organs. = bicep muscles Different combinations of these tissues are assembled to form organs Epithelial Tissue: 2 components 1. Epithelia ◦ Cover exposed surfaces and line internal cavities and passageways; they often contain secretory cells, or gland cells, scattered among other cell types. ◦ Example: digestive tract, stomach intestine, anus, etc. (a long tube), basically they are covered by a lining made of epithelial tissue 2. Gland cells ◦ Derived from epithelial cells ◦ But secretory cells will predominate more on areas where its just a gland. ◦ Two types: ‣ Exocrine (outside) : secrete onto external surfaces or into internal passageways (ducts) that connect to the exterior. ‣ Endorcrine (inside): secrete hormones or precursors into the interstitial fluid, not directly secreted to the external areas of the body, usually directed to the blood stream, or into the fluid between cells (interstitial fluid.). Kept within the body and secreted within the body. *in the diagram above, it looks like a photo from the intestine, there are scattered mucus goblet cells that secretes mucus that will help lubricate food as they pass through the digestive tract. Epithelial tissue forms: the covering on body surface (e.g skin) The lining of body cavities or tubes (e.g serous [pleural membrane] or mucous membranes [membrane infused with goblet cells]) The glandular tissue of the body, they are interspersed (e.g most endocrine glands) Epithelial tissue can function to protect (the skin protects), absorb (intestine), filter, and secrete, but usually is specialaized to one or two functions this tissue is classified by the number of layers and by its cellular shape. Columnar = the cells from the side looks like a column. Simple = one layer thick Squamous = squashed Epithelial cells are all hexagonal on Stratified = many layers thick. Cuboidal = cube shape from the side top view. Epithelial: Have one exposed or apical surface - have polarity (this means they have two different sides) ◦ The skin is exposed to the outside world from one side ◦ Another example is that the intestine is exposed to the food that pass by coming from the outside environment. Basal surface the deeper structure compared to the apical surface. ◦ Is attached to a basement membrane (basal lamina) = sticky, non-cellular membrane (no cells). ◦ Sticky because its made of glycoproteins and polysaccharides ◦ Anchors epithelial to connective tissues. It is gel-like. Are avascular = no blood vessels penetrating them ◦ How do nutrients in cell reach them to keep them alive? ‣ The connective tissue underneath is vascularized, epithelial therefore realized on diffusion! Are innervated (they have nerves) = to detect things like touch and vibration. Simple columnar epithelial tissue: One layer and has a column shape Functions of Epithelial Tissue 1.) Physical Protection from abrasions, dehydration (we are 70% water, big role of the skin to protect you from dehydration), and chemical or biological agents 2.) Control Permeability how much material can pass through to deeper materials of the body. Skin cells are very impermeable to water. Water would not vaporized outside of the body. (Very important!) epithelial cells differ in the degree that ions, proteins, hormones, nutrients can cross to deeper areas of the body. 3.) Provide Sensation most have large sensory nerve supplies Neutoepithelia (Specialized tissue) ◦ tissue contains cells that sense smell, taste, sight, equilibrium (help detect if head is balanced in space)and hearing Provide pressure and temperature sensations 4.) produces Specialized secretions - gland cells; epithelial that secrete Specializations of epithelial cells microvilli - absorption, increase surface area of the cell by 20x Cilia - (there for movement) 250 cilia/cell coordinated beating moves mucus, injured by smoke, abrasion, and disease. ◦ Windpipe = mucus is there to catch debris not to enter cells. Maintaining the Integrity of Epithelial Tissue 1. Intercellular connections = so thats cells are not falling out of your body. 2. Attachment to the basal lamina 3. Maintenance and repair - stem cells, epithelia germinative cells located near basal lamina skin cells only last for 30 days, they need cells that are going through rounds of cell division. Intercellular connections: epithelial cells attach to one another and extracellular fibres of the basal lamina plasma membranes attach through transmembrane proteins called CAMs (cell adhesion molecules, Cadherin, integrin) Intercellular cement - made of proteoglycans (sticky protein material) Cells junctions ◦ Adhesion belt ◦ Tight occluding junctions (interlocking proteins and lipids) ◦ Gap junctions (interlocking channel protein “connexons” that allow ion transport; necessary for muscle contraction and cilia synchronization) ◦ Desmosomes (spot desmosomes and hemidesmosomes) (aka Macula adherents) - consist of CAMs to link plasma membranes. ‣ Desmosomes = most abundant connection between cells in the superficial layer of the skin Occluding Junction at a tight or occluding junction, the lipid portions of the two plasma membranes are tightly bound interlocking together by interlocking transmembrane proteins. It does not let materials slip between cells Cyngembrane Adhesion Belt encircles cells and binds them to their neighbours through bands of dense transmembrane glycoproteins (cadherin) attached to micro filaments (actin) goes alund Mf Microfilaments creates the terminal web thecell Gap Junction Forms channels, not found in intestinal cells Made up connexons (6 connexine proteins) that form a narrow passageway and let’s small molecules and ions pass from cell to cell Found in cardiac tissue and smooth muscle tissue. The ions coordinate the cells, (e.i all the cells have to contract the same time to create a beat) Spot Desmosomes Keratin have intermidiate filaments typically Keratin, of the cytoskeleton. Increases the resistance of the tissue to mechanical stress. CAM Cadherin ◦ A cell adhesion molecules (CAMs) are transmembrane proteins that bond to each other and to extracellular materials. The membranes of adjacent cells may also be bonded by intercellular cement, a thin layer of peptidoglycan Why are they only found in spots? ◦ Allows stretching and twisting within the tissue without causing damage. ñE ◦ When you twist you skin, your skin will rebound to its place. ◦ Prevents damage! hemidesmosome Hemidesmosome which attaches the deepest epithelial cells to the basal lamina I Also base keratin of the cytoskeleton Basement membrane ◦ Is a complex structure produced by the basal surface of the epithelium and the underlying connective tissue. ◦ Clear Layer (lamina Lucida/basal lamina) = contains glycoproteins and a network of fine protein filaments. ◦ Dense Layer (lamina densa/ reticular lamina) = contains bundles of coarse reticular fibres, giving the basal lamina its strength and acts as a filter that restricts diffusion between the adjacent tissues and the epithelium. 1.) Simple Squamous Epithelia simple = one layer thick; squamous = looks like a squash Very thin, ideal location for diffusion Specialized for diffusion (exchange of substances) and filtration Places you can find it is: Lining of the blood and aveoli of the lungs ◦ We want quick diffusion of gas in blood cells. ◦ Oxygen that comes onto the lungs needs to be exchanged quickly. Forms the alveoli, capillary walls and the endocardium. Also line body cavities that are not open to the outside (we don’t want it outside of the body cause its too thin), wher they are part of serous membranes Functions ◦ Reduce friction = they are part of the serous membranes 1 ◦ Regulate fluid composition - permeability, absorption, and secretion Mesothelia = epithelia in the middle part of the body Endothelia lining heart and blood vessels = inside lining of the heart basically Paracellular transport fewer junction substance passes through the narrow space between cells Transcellular transport substances enters the cell via active or passive means (like when oxygen enters the alveoli) Substances diffuse through the cytoskeleton Substances exits the other surface of the cell via active or passive means. 2.) Stratified Squamos Epithelia stratified = means multiple layer; squamous = squash shape Most common stratified epithelia Is what makes the skin and other internal linings that are exposed to material from the outside world. Specialized for protection, and is found in high use areas where abrasions can occur -> lines the mouth, esophagus, and outer layer of skin (keratinized) = skin becomes as though and dry because its packed with keratin (fibrous protein) they preven body from dehydrating and keeps cell durable. tyiiiiiaes.it The apical surface contains squamous shaped cells, whereas, the deeper cells may be for harder microorganisms cuboidal or columnar. topenetrate ◦ The reason why the bottom looks more columnar is because they are less packed with keratin and are stem cells and will go through more rounds of division. As surface cells are rubbed away, they are replaced by mitotic division of the basal cells (which are stem cells), the daughter cells will then get pulled up. 3.) Simple Cuboidal Epithelia simple = one layer thick, cell is cubed Specialized for absorption and secretion through lining glands and ducts Thyroid glands = secrete thyroid hormones Kidney tubeless = their job is to clean blood. They are made of nephrons that are made of simple cuboidal epithelia. One cell thick is essential for secretion 4.) Stratified Cuboial Epithelia multiple layer thick, cubed shape Fairly rare, think about sweat glands Sweat will be secreted when it is hot! 5.) Transitional Epithelia tolerates repeated compression/stretching Because the shape of the cell changes Think about urinary bladder ◦ The bladder changes, as the bladder is empty the shape of the cells are relaxed and look fairly columnar. ◦ When the bladder is filed up the cells are flattened and they look more flattened, like a cube or squamous. They tolerate repeated stretching and compression. 6.) Simple Columnar Epithelia specialized for absorption and secretion a Line the digestive tract from the stomach to the anus Contains glandular cells called goblet cells that produce a lubricant called mucous This gives epithelial lined cavities that are open to the outside the name mucous membranes. 7.) Stratified Columnar Epithelia more than one cell thick, and columnar shaped Found in salivary gland duct We always use apical layer name. E 8.). Ciliated pseudostratified columnar epithelia a convoluted apical plasma membrane forms the motorized cilia, that aid in debris removal All cells rest on the basement membrane, but some are shorter than others. Gives rise to the term pseudostratified. Lines most of the respiratory tract Secreted mucous collects debris and cilia proper it superiorly (to remove unwanted debris out of actually the body) layer one Exocrine Glands secreting to the outside world A. Merocrine ◦ Ex. Mucus production (goblet cells, saliva cells) ◦ What happens is the the genes that are transcribed to make proteins to make mucous, are then packaged to secretory vesicles which would then exocytosed (vesicle fuses with plasma membrane and secrete the package outside). B. Apocrine ◦ Mammary glands = uses both merocrine and apocrine ◦ Same idea proteins will be transcribed, there are also carbohydrates and fats that would be moved to the apical surface of the exocrine gland cell. ◦ The apical surface then breaks off (this is what actually makes the milk) ◦ Plasma membrane seals over and the process starts again. C. Holocrine ◦ Sebaceous gland (hair follicle) = produce oil/sebum ◦ Stem cells are at the base, cells produce secretion, thus increasing its size. ◦ As the cells become more full of the oil, the cell will die and burst and thus producing oil in the surface of the skin. ◦ This happens, the stem cells continue to create daughter cells. Most of your sweat glands are called eccrine and secrete a clear, odourless substance (mostly water and NaCl). What method of secretion does a eccrine sweat gland use? Merocrine! There are other sweat glands produced by the body: Armpit = Apocrine sweat glands (that what they called them) they just call it like that but they are still merocrine. they have more bacteria and smelly The protein is food for the bacteria which makes is smelly! Connective Tisuse consists of: A. Cells - fibroblast, macrophages, mast cells, plasma cells, adipocytes, and white blood cells. The others are known as immune cells that ◦ They are spread out compared to the epithelial cells B. Extracellular matrix (ECM) - makes the bulk of CT ◦ They are located outside of the cell ◦ They have fibrous proteins (collagen and elastin), ground substance (proteoglycans) - they are produced by fibroblasts ◦ Ground substance - clear colourless, sticky syrupy (because of the proteoglycans) C. Tissue Fluid (ground substance) ild ◦ Clear and colourless ◦ Viscous fluid and proteiglycans = reasons why they are sticky connective tossieu is found to varying degrees in the different organs (e.g lots in bone and skin, but very little in the brain) Connective tissue serves to ◦ Bind and support (e.g ligaments, tendons, and bones) ◦ Protect (e.g bones and cartilage, adipose tissue) ◦ Store and insulate (e.g adipose tissue) ◦ transport (e.g blood) Characterized by an intricate extrcaellular matrix, that has large amounts of collagen fibres (provide tensile strength), and elastin fibres (provide resiliency) Connective tissue can be vascular (w/ blood vessels) or avascular (no blood vessels = they rely on diffusion). Tendons and ligaments tend to be avascular, and as a result heal very poorly. There are six general types of connective tissue: ◦ Loose ◦ Dense CT ◦ Cartilage ◦ Bone ◦ Blood ◦ Lymph Connective Tissue Proper Contains cells (fibroblasts - secrete ECM proteins, adipocytes, macrophages - scavengers (immune cells) and mesenchymal cells - stem cells that can divide to produce fibrocytes (mature fibroblasts), macrophages, and or other cells.) Loose A. Areolar tissue E.g between skin and muscle contains both collagen and elastin fibres, loosely arranged Forms basement membrane for epithelia tissue, and mucous membranes This tissue swells with the release of fluid from the blood stream, a condition called edema. Contains ◦ Melanocytes = is a fixed pigement cell that synthesizes melanin, a brownish yellow pigment ◦ Fixed macrophages = engulfs cell debris and pathogens ◦ Mast cells = stimulates local inflammation and mobilize tissue defenses ◦ Fibroblast = synthesize extracellular fibres ◦ Adipocytes = stores fat cells, stores triglycerides. ◦ Collagen fibres in beige = resist stretching , elastic fibres in blue = allow stretching. ◦ Reticular fibers = gives stability. ◦ Plasma cell - is an active, mobile immune cell that produces antibodies ◦ Free macrophages = wandering phagocytosis cells that patrol the tissue.  ◦ Mesenchymal cells = stem cells that participate in tissue repair ◦ Neutrophils and eosinophils = phagocytotic blood cells that enter the tissue during infection ◦ Lymphocytes = mobiles cellls of the immune system. ◦ Capillary that are carrying blood. ◦ Ground substances B. Adipose tissue largely adipocytes Functions as padding and insulation Deep to the skin especially at sides, buttocks and breast Stores energy C. Reticular Tissue has a lot of reticular fibers = net that provide scaffolding and support ◦ Liver, kidneys, splee, lymph nodes, and bone marrow ◦ Provides supporting framework. Three types of DENSE Connective Tissues Dense CT contains mostly collagen or elastic fibers in its matrix, closely packed Dense Regular CT forms tendons (muscle-to-bone connections) and ligaments (bone-to-bone connections) are poorly vascularized, and deep fasciae around muscle which is highly vascularized parallel matter = I order to direct the forces as the tension builds as muscle contracts Dense Irregular CT is found in dermis, visceral organ capsules, perichondrium (tissue that surround cartilage), periosteum (tissue that surrounds bone) Has irregular, we want to withstand the tension that is applied when someone pulls the hair for the skin in whatever different directions. Elastic eg. Elastic ligaments between vertebrae, walls of large blood vessels (aorta) Elastic instead of collagen, parallel as well to withstand the forces being applied to that. *fibroblasts are there because its what produces the fibers (collagen or elastic) Fluid Connective Tissues - Blood and Lymph the continuous circulation of extracellular fluid, including the fluid connective tisssue called lymph Waterless Capillaries are the smallest and most delicate blood vessels. ation All exchange betweeen the blood and interstitial fluid occurs at the capillaries. At capillary networks, blood pressure forces water and small solutes out of the bloodstream and into surrounding interstitial fluid. lymphvessels Lymph forms as interstitial fluid enters the lympahtic vessels. Lymphatic vessels form a network that returns lymph to large veins near the heart. = delivers oxygen Clotting, Immune natural Plasma = matrix, no system cells band aid. ropes proteins Lymph = has white blood cells Supporting Connective Tissue cartilage ◦ Cells (chondorcytes) are in cavities called lacunae, and produce collagen in a gel-like matrix ◦ Cushions the end of long bones (humerus, femur) [protect from bone and bone contact], form epiphyseal (growth plates) and intervertebral discs. ◦ Cartilage is avascular, and must receive nutrients through diffusion ‣ Hyaline End of all long bones, red places are growth plates Synovial joints = movable joints Nose has hyaline cartilage and between two nostrils Provide stiff but somewhat flexible support; reduces friction betweeen bony surfaces ‣ Elastic Elastic fibers in the matrix Think EEE = (ear and epiglottis) growthupward Ear is all elastic cartilage, epiglottis prevents food from going to the wind pipe ‣ Fibrous Intervertebral discs Lots of collagen in the gel matrix = more durable Prevents bone to bone contact, resists compression, limits relative movement, shock absorption. middle ◦ Cartilage has surrounding material calle Perichondrium ‣ Around the perimeter of all 3 types of cartilage ‣ 1. Outer fibrous layer of dense irregular CT ‣ 2. Inner, cellular layer (fibroblasts + chondrogenic cells) stem cells for chondrocytes Bone ◦ Has osteocytes as its cells ◦ Contains a very hard matrix of calcium salts and a large number of collagen fibres ◦ Bone cells called osteoblasts (immature) and osteoclasts reside in cavities called lacunae ◦ Bone is quite vascularized (bleed lots/heal faster than cartilage) ◦ Hollow cavity = major site of hematopoiesis (hema = blood; production of ) ◦ Only a small volume of bone is ground substance ◦ 2/3rd of matrix is calcium salts (calcium phosphate) and the rest is collagen fibers and 2% is cells. ◦ Periosteum is same as perichondrium, surrounds the outer area of the bone 4 types of Membranes 1. Mucous A. Find in the digestive tract (small intestine) = simple columnar epithelia B. Lubricate the food to make sure it pass through the digestive tract C. Lamina propria (areolar tissue) = connective tissue proper (LOOSE) 2. Serous A. Membrane the surround the lungs and the heart and visceral organs B. Mesotheliun C. Serous fluid = transudate = no friction when the lungs are moving D. Areolar tissue 3. Cutaneous A. Skin B. Stratified squamous epithelial tissue C. Areolar tissue D. Dense irregular CT 4. Synovial A. Movable joints epithelium = simple squamous B. Synovial fluid C. Areolar tissue Fasciae connective tissue layers and wrapping that support and surround organs Superficial fascia between skin and underlying organs Areolar tissue and adipose tissue Also known as subcutaneous layer or hypodermis Loose CT; provides insulation and padding Deep Fascia forms a strong, fibrous internal framework Dense connective tissue Bound to capsules, tendons, and ligaments Dense CT; layers like plywood providing resistance Subserous fascia Between serous membranes and deep fascia Areolar tissue Loose CT; provides padding Nervous Tissue Nervosu tissue is considered to be ‘excitable’ due to its ability to transmit electrical impulses Nervous tissue consists of neurons (cells that convey electrical impulses) and a number of accessory cells called glial cells Neurons often transmit their signals to other cells through a chemical messenger called a neurotransmitter Functions of neuroglial maintain physical structure of neural tissue Repair neural tissue framework after injury Perform phagocytosis Provide nutrients to neurons Regulate the composition of interstitial fluid surrounding neurons. Muscle Tissue consist of specialized contractile tissue supported by connective tissues sheaths, and are considered ‘excitable tissue’ Muscle cells are also called muscle fibres because of their shape Three different types of muscle tissue: skeletal, cardiac, and smooth Skeletal muscle cells are long and thin, and have visible bands or stations Due to their shape, skeletal muscles cells are called muscle fibres Each fibre is multinucleated probably due to thei length Fibres are pancaked by connective tissue to form individual muscles. This connective tissue covering forms the tendon, which attaches the muscle to bone Under voluntary control, stimulated by neurons Cardiac Muscle this tissue makes up the bulk of the heart Also stratified, however they differ from skeletal muscle fibers in that they are smaller, shorter, uninucleated, branching fibers. Cardiac muscle fibers fit tightly together with intercalated disc or gap junctions which allow the heart to contract in synchronized fashion These cells contain up to 35% mitochondria Cardiac muscle is under involuntary control Smooth Muscle cells are small, uninucleated, and have no visible striations Found in the walls of hollow organs, such as stomach, the bladder, the uterus, and the vessels (blood and lymph) Smooth muscle contractions causes the organ diameter to reduce and relax to increase dilation. Smooth muscle contracts much slower than the other muscle types Smooth muscle is vital in the regulation of blood flow, blood pressure, and in moving foodstuff through the digestive tract (peristalsis) Response to tissue injury involves inflammation and regeneration Sometimes there is autolysis = depends on the injury 1. Damage cells release the 3Ps = prostaglandins; proteins, and potassium which stimulates the mast cell 2. Mast cells when activated releases = histamine, heparin, and prostaglandins 3. This stimulates inflammation A. Increased blood flow = blood vessels dilate B. Increased vessel permeability C. Pain 4. Increased focal temperature A. Increased oxygen and nutrients B. Increased number and activity of phagocytes C. Removal of toxins and waste products 5. Fibroblasts produce a scar tissue (collagen fibers) if wound is deep or large 6. Mesenchymal stem cell division = regeneration The Skin as an Organ = Cutaneous membrane The skin consists of 2 primary layers superficial to a supportive layer 1. Epidermis (no blood vessel) - a special type of stratified squamous epithelial tissue that produces large amounts of the fibrous protein keratin (keratinized). The epidermis is tough and protective, but relies on the dermis for nutrients 2. Dermis - is made up of dense connective tissue that is cell vascularized and contains sweat and oil glands, and sensory receptors Hypodermis (subcutaneous tissue) contains adipose tissue that serves to insulate our bodies, and anchors the skin to underlying structure Skin Aging and Repair During the aging process, skin looses elastic fibres from the dermis and the subcutaneous tissue diminishes, causing skin to wrinkle and sag. Skin becomes dry as glandular activity declines. Decreased ability to lose heat as blood supply to dermis is reduced Macrophages and immune cell population decrease to 50%. Skin repairs can be twice as slow. Muscles & bone weaken in part due to 75% decrease in vitamin D3 production which affects Ca2+ & PO4 absorption Decubitus ulcers- pressure sores occurs when pressure is continually applied to skin, soft tissue, muscle and bone in excess of the capillary filling pressures, 32mmHg. This can lead to irreversible tissue damage. Stretch marks: tearing of the dermis due to extreme stretching (e.g. during pregnancy), leaving visible lines (striae)