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Notes lecture about skin...

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Lecture 1: Tissues and Epithelia Tissues overview:  Groups of cells that are similar in structure and perform a common function  4 Primary tissue types are found in the body - Epithelia: covering - Muscular: movement - Nervous: control - Connective: support (bone is a type of this tissue)  The 4 primary tissue types, put together make up everything (structure) in your body Epithelia  Covering, lining and glands (it’s secretory) - Barriers (In order to get through the skin, have to pass through the epithelium) - Highly cellular, forms sheets which allows them to cover and line things - Cells all in close contact with o Tight junctions: They make the cells cling onto each other really tightly and stop substances from travelling between cells o Desmosomes: particularly important in small layers of skin – don’t want skin cells to fall apart if you put pressure on them (get whole heap desmosomes in the skin) o Gap junctions: allow small substances to pass between adjacent cells  Polarity –they have a ‘right way up’: they have a surface which is either on: - The free surface – open to a space inside your body or open to outside (all epithelia have a free surface) - The Basal surface –which is closest to the bottom of the epithelia which sits on the basement membrane (lamina) - Lateral surfaces –which in a single layer of epithelia would be in contact with the adjacent cells  Basement membrane (basal lamina) - An a-cellular structure, which consists of lots of protein polysaccharide complexes: proteins together with sugars (typical of all epithelia)  Connective tissue: Epithelia are a-vascular –don’t have blood vessels within the epithelium - The connective tissue underlying is well supplied with blood vessels, supports them, gives nutrients and takes away wastes by diffusions away/into the epithelium  Vascularity and Innervation - If it is going to form a surface, you want information about things in contact with that surface - You therefore want good innervation  Regeneration - They divide very well - On a surface you likely to be affected by acids, bases, digestive enzymes, things scraping along your skin (like inside your mouth)

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Cells are going to get damaged or knocked off: so you need to replace them fairly regularly Also a protective function –it helps to reduce ability for infectious substances to get in there if the cells a constantly falling off

Muscular Tissue  Contractility –produces movement in the body  Highly cellular  Well vascularized (good blood and oxygen supply and more nutrients)  Cells contain myofilaments - Actin and myosin –highly organized in way that can allow movement outside of the muscle (like limbs etc) not just of the muscle itself - Muscle is excitable: responds to a range of electrical or chemical stimuli Nervous Tissue  Makes up nervous system  Concerned with communication and control  Highly cellular  2 major cells types: - Neurons: generate and conduct nerve impulses (excitable) - Supporting cells - Glia: glue that supports the supporting cells together Connective Tissue  Most widely variable of tissues  Many varied functions - Expressing different genes, making different proteins and making different intracellular substances which allows it to perform its functions - Functions include: binding things together, support, protection (bones of skull protect the brain), insulation (fat insulates), transport (blood is a connective tissue transporting cells, nutrients, oxygen around)  Common (mesenchyme) origin - An embryological, basic, prototype connective tissue - Cells then differentiate into different cells, end up with wide variation in the tissues  Extracellular matrix separates cells - Widely separated - Extracellular matrix separating the cells - Can determine if it’s a connective tissue: nuclei are too far apart for the distance to be explained by a cell body  Degrees of vascularity - A-vascular: have no blood vessels at all (cartilage) - Those that are very well supplied with blood (fats and bone) Lecture 2 Classification of epithelia 

Shape of cells - Squamous –flattened - Cuboidal

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- Columnar Number of layers of cells - Simple –single layer - Stratified –multiple layers

Types we can get from such classification:  Simple squamous  Simple cuboidal  Simple columnar  Stratified squamous  Stratified cuboidal (rare)  Stratified columnar (rare)  Pseudostratified columnar (specialized type)  Transitional (specialized type) Simple squamous  Single layer of cells which are flat (actually look a bit like a poached egg)  They have a flattened nucleus lying parallel to the surface of the epithelium  Form a simple barrier, but they are not protective and are found in areas where filtration or rapid diffusion is a priority - In alveoli of the lungs, filtration membrane of the kidneys, line capillaries, line all blood vessels, - Smoking damages the junction between the epithelium pushing it of the basal membrane Simple cuboidal  Single layer of cuboidal cells  You can see the nucleus (has a central spherical nucleus)  Both secretory and absorptive functions (it may have microvilli) and have a folded membrane - In some of kidney tubules (where you take back a lot of things) and require a larger surface area, may have lots of microvilli - Found in the secretory portions (that are actually doing the secretions) and the ducts (the bit that takes the secretion across to the surface of small glands) - Larger glands tend to be stratified cuboidal or stratified columnar  Also found on surface of the ovary Simple columnar epithelium  Number of layers either ciliated or nonciliated  Shape of cells –tall cells, sausage shape nucleus, microvilli on some of them  Surface specialisations  Typically found lining the gut (stomach to the rectum)  Evidently lots of capillaries Pseudostratified columnar  Single layer of columnar cells varying in height –some reach, some don’t reach the surface  Nuclei sit at all sorts of different levels

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Many have specialized surface –tend to get cilia and also tend to get goblet cells Found lining most of respiratory tract - Goblet cells putting mucus out and catches all bits of dust and grot that gets inhaled and the cilia waft that away up and to the back of your throat

L3 Stratified epithelia Stratified squamous  Upper most layer of cells (closest to the lumen) are flat and squamous  Concerned with protection (areas of wear and tear and where abrasion may take place –like inside of mouth)  Keratinized –surface cells have the fibrous protein keratin, making the cells tough - They lose their nuclei (die) - Epidermis of skin is all Keratinized  Nonkeratinised –also found in areas of ware and tare (oral cavity, esophagus, the vagina and anus) - Tend to line moist areas –wet epithelium - No keratin Transitional epithelium  Water proof epithelium found in all places where urine is travelling or stored - Kelasise (first tubes that the urine travel through from the kidney) which empties into the ureter (carries urine from the kidney to the bladder), the bladder (bag holding the urine), and then urethra (tube from bladder to the outside) - All of these structures are lined with transitional epithelium  2 forms, stretched and non-stretched form - In the bladder as it fills, it gets stretched (other tubes don’t stretch)  Cells have round nuclei giving bulging surface appearance - When stretched, these cells able to slide over one-another so that you end up having, rather than 5 or 6 layers, having only a couple (initially multiple layers however once stretched becomes only a couple) L4 Connective Tissue Characteristics  Extracellular matrix separates cells - Outside the cells  Most widely variable of tissues  Many varied functions  Common (mesenchyme) origin - All connective tissues come from mesenchyme which is a primitive tissue in the embryo and fetus  Degrees of vascularity - Some are really well supplied with blood vessels

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Some have no blood vessels

Functions:  Found throughout the body  Binding things together (epithelium might need to be bound down to the structures underneath)  Support (fat, bones and cartilage)  Protection (bone, fat)  Insulation (fat)  Transport (blood is a connective tissue and transports all sorts of things around your body) Structural elements allowing the connective tissue to perform various functions  Fibers –various sorts of proteins providing support and are secreted from the cells - Collagen o Extremely tough o High tensile strength (if you pull the collagen fibers long ways they actually have the strength of steel) o They are not elastic and don’t bounce back - Elastin –elastic fibers o Able to be deformed but can bounce back to original form - Reticular –slightly different chemistry o Similar to collagen in that they form fine branching collagenous type fibers o Particularly concerned with forming networks to support soft structures in soft tissues of organs (form like a sponge of these fine fibers)  Ground substance –in between cells containing both cells and fibers - Amorphous –unstructured, clear and fairly sticky - Acts as molecular sieve –sorts things travelling through it, out o Small water molecules are permitted to go through quickly (rapid diffusion) o Movement of large molecules/bacteria inhibited (useful because they are usually toxins that you don’t want) - Consists of o Interstitial fluid o Cell adhesion proteins (glue) –actually on the cells themselves, so they glue the cells within the ground substance and most cells not free to move around o Proteoglycans –sugar and protein (look a bit like a bottle brush, protein down the middle like Hyakuronic acid, and then have proteoglycan which have a core protein and chondroltin sulfate which trap water o The more water there is, the stiffer the ground substance is  Connective tissue cells - Each class of connective tissue has a fundamental cell type that exists in an immature and mature form

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Undifferentiated gets suffix ‘blast’ o Actively mitotic o Secretes fibers and ground substances - Once they synthesize the matrix they assume their less active mature mode indicated by the suffix ‘cyte’ o Mature forms can revert to the immature form if the matrix is injured and then can go back to being the mature form Types of connective tissue - Connective tissue classes and subgroups - General (fibrous) connective tissue = Connective tissue proper - Specialized Connective tissues o Skeletal tissues (bone and cartilage) o Adipose tissue o Lymphoid tissue o Blood Cells in ‘prototype’ Connective tissue - Loose connective tissue or areola connective tissue o Tend to get all three, Collagen, Elastin and Reticular fiber types o Fibroblasts –the mature form o Fat cells/adipose sites –if you empty out a fat cell (take fat out by using the energy in there) they go back to looking just like fiber blasts o Cells that migrate in from the blood –white blood cells of various sorts and other cells concerned with tissue response to injuries o Get neutrophils, eosinophils and lymphocytes o Get cells concerned with response to injury which are masked cells containing heporine and histomenes o These sort of cells cluster in spaces deep to the various epithelia in the body or along blood vessels –places where things might be getting in, infection travels around the blood o Macrophages are large phagocytes that have come from monocytes in the blood o Langerhan cells are macrophages (just some of them get special names) o Plasma cells come from B lymphocytes (activator cells that make antibodies –immune response)

Connective tissue proper (fibrous connective tissue) 2 subgroups: classification based on fiber arrangement and density  Loose Connective tissue - Areolar o Binding body parts together while allowing them to move freely over one another o All three fiber types loosely distributed throughout and widely packed o Lots of fiber blasts and macrophages, occasional fats cells

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Reticular (mainly found in cellular organs like the liver providing support for cells) o Lots of reticular tissue, with lymphocytes (the white blood cells in between) o Fibers predominantly reticular fibers o A mesh-work –forms a sponge with fiber blasts in there, forming an internal framework to support free cells in some organs (liver, spleen, bone marrow and lymph nodes Dense Connective Tissue Dominant fiber type is collagen (dense because the fiber occupies more space than the fibers around them) - Dense regular o Fibroblasts (cells making the fibers and the ground substance) appear as the flattened cells between thick layers of collagen – has flattened nuclei o Collagen all runs in the one direction o These form the tendons of muscles/ligaments at joints o Don’t allow much stretch: can stretch them out (loose waving appearance) but won’t go any further - Dense irregular o Has the same structural elements of regular connective tissue however collagen bundles are orientated in many different directions o Tend to form sheets of tissue mainly in places where tension is exerted in many different directions –dermis of the skin, cant pull it up, but can pull it crossways (like at elbow joint etc) o Also forms joint capsules (around a synovial joint) which helps hold the bone together and allow movement in certain directions o Also forms fibrous capsules of many organs

L5 Specialized Connective Tissue Adipose Tissue  Areola tissue (loose connective tissue)  Modified to store nutrients –stores fat droplets which is an energy store  Predominant cell type are adipose sites –closely packed (cytoplasm basically full of a large fat droplet with very little matrix)  If you empty fat droplet out of them: they look like fibroblasts  Areola tissue can always turn into adipose tissue  Very good blood supply –has high metabolic activity taking nutrients out of the fat and putting them in the blood  Found in subcutaneous layer –immediately underneath the skin: here it can contribute to some of the sexual differences between males and females  Also found around the kidneys and eyes –called structural fat which can only be dissolved in extreme starvation  Absorbs shock and insulates  Pads various parts of body –like buttocks  They don’t have any of the characteristics of the other 3 tissue types - They don’t move (respond to things the way muscle does)

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They don’t have specialized junctions between them as they are not forming a surface and don’t require barriers Lymphoid Tissue (not going to go into much detail –don’t really need to know much more than it is a connective tissue) Blood  Blood cells in non living matrix: the plasma  Fibers in blood are soluble proteins which only become visible during clotting  Function of transporting things around –scatters hormones, delivers nutrients etc. Cartilage  Proteoglycan molecules: lots of glycosaminoglycan (like for e.g. chondroitin sulfate and hyaluronic acid) and adhesion proteins  Avascular –relies on diffusion from the perichondrium (connective tissue membrane on the outside –a bit like a capsule) for its nutrients  Limit to how thick cartilage can be: limit to effective diffusion distances, which is what limits the thickness of cartilage –usually in fairly thin sheets  Cells found in groups in little spaces between the cartilage  Classified somewhere between dense connective tissue and bone - Its tough, but has a little bit of flexibility - More supportive and can attach muscles, tendons and ligaments to it and move it in the same way as bone  Cells take the prefix ‘chondro’ and you can get chondroblasts which are the immature form and chondrocytes which are the mature form  Ground substance has firmly bound collagen fibers –depends on the type of cartilage as to how many collagen fibers there are and whether or not they are visible  Contains a lot of tissue fluid -80% water: which is a reason why we have so many glycosaminoglycan’s as they are able to bind all the water making it stiff (which is what makes it a very firm structure)  No blood vessels or nerves –makes it very good for joints  Covers the moving (articulating) surfaces of bones  Perichondrium is dense irregular connective tissue that surrounds the cartilage - Tends to contain chondroblasts which can add onto the surface of the cartilage and turn into chondrocytes - Also contains blood vessels  Able to grow by both interstitial and appositional means - Interstitial means that a cell in the cartilage matrix can actually divide, and the matrix is fluid enough for the two new cells to push away from each other and put more cartilage matrix in between them (grows from the middle out) - Appositional means adding more cartilage: as cells divide, add more cartilage onto the outside  3 types of cartilage: 1. Hyaline cartilage  Means glassy –has a clear, pale pinky/blue matrix

Lots of collagen fibers Very good at resisting compressive forces (nice and firm and wont flatten) Found on articulating surfaces of joints on bone, also in the bones of the larynx, trachea, bronchi and on growth plates  Forms the bone model where a lot of our bones develop from  Chondrocytes live in little holes amongst the matrix  Isogenous nests - Individual cells in a lacuna (whole in the matrix) - They lay down more matrix when dividing: gradually push apart meaning this particular part of the cartilage gets to be a bit thicker - Isogenous nest means a group of cells that all came from the same cells, which is laying down more matrix 2. Elastic cartilage  Elastin fibers  Occur where things are going to get distorted –e.g. the epiglottis where food going down knocks the epiglottis (a flap that bounces back up again) and the pinna of the ear (flappy part) 3. Fibrocartilage  Collagen fibers  Alternating rows of chondrocytes and then a row of collagen fibers  Found in areas where twisting or shearing forces occur –e.g. between the vertebrae in vertebral column: bend forward, bend backward and side-toside - Also disk between jaw –temporomandibular joint to allow chewing, etc.  Collagen fibers running in one direction with rows of chondrocytes, has rounded cells (different to other cartilage which are flattened) living in lacunae –this is defining feature   

L6 Bone: 2 ways to look at bones: 1. As an osseous tissue 2. As an organ of the body  Organs contains many sorts of connective tissue: marrow, cartilage, adipose tissue, nervous tissue, fibrous connective tissue  Simple connective tissue: cells contained in matrix which is hardened by the deposition of calcium, salts, and other minerals –this process is called mineralization or calcification  Main function as support, protection, place of rigid attachment for levers like muscles (movement)  Marrow involved in blood formation  Functions in electrolyte balance –particularly calcium and phosphate ions travel in and out of bone  Functions as a base balance: alkaline, phosphate and carbonate salts that act as buffers to help maintain the pH of the rest of the tissue of body at right level for cells to function properly  Functions as detoxification; toxins picked up are released from the bone into the blood at a rate that the body can deal with –e.g. lead poisoning  Long bones: humorous, femur and bones of fingers  Typical set of features

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Covered by Periosteum which is a dense, irregular connective tissue Contains lots of collagen: outer layer of dense connective tissue contains lots of collagen, and inner layer which contains osteogenic cells (where cells are able to turn into bone cells live) - Inside bone (marrow cavity and little holes in the layer covering spongy bone: layer called endosteum (which is a reticular tissue) - Collagen fibers important as muscles attach to bone, and collagen of the tendon in the muscle blends with the collagen in the Periosteum and actually poke down into the bone called sharpie fibers - A shaft diaphysis through the middle made of compact bone - Ends called epiphysis (one proximal –close to end that joins to body and one distal) made of spongy bone ...