Anatomy Notes - Tissues

Tissues

  • Four major tissue types:

    • Epithelial tissue - boundaries, lines internal and external body surfaces, creates division.
    • Nervous tissue - brain, spinal cord, nerves; monitors internal and external environments, allows responses based on changes.
    • Muscle tissue - responsible for moving body and moving things through body spaces.
    • Connective tissue - most variable type. Examples: adipose (soft), bone (hard), blood (liquid). Supports and connects body structures.

  • A tissue is a group of cells working together.

  • An organ is multiple tissues working together for specific body function.

    • Most organs have all four tissue types. Example: heart (nervous, epithelial, connective, muscle).

Epithelial Tissue

  • Sheets of cells cover internal and external body surfaces.

  • Forms the base of certain glands (sweat, oil, thyroid).

  • Epithelium has a "first and last name".

    • First name: number of layers
      • Simple: one layer
      • Stratified: multiple layers
    • Last name: cell shape
      • Squamous: flat, pancake-like
      • Cuboidal: cube or square shaped
      • Columnar: tall and skinny

  • Examples:

    • Multiple layers of cuboid cells: stratified cuboidal
    • Single layer of flat cells: simple squamous

  • Exceptions to naming scheme:

    • Pseudostratified (respiratory passageways)
    • Transitional (bladder)

Simple Squamous Epithelium

  • Single layer of flat cells
  • Not a very good barrier
  • Allows rapid diffusion
  • Examples:
    • Alveoli in lungs (oxygen absorption)
    • Capillaries (nutrient exchange)
    • Serous membranes (pleura, pericardium, peritoneum)
  • Capillary exchange:
    • Capillaries have a single layer of squamous epithelial cells.
    • Easy for sugar, oxygen to diffuse out.
    • Easy for waste to diffuse back in.
    • Medication absorption occurs from site of administration into the blood. Oral drugs dissolve and pass through epithelial cells. Intravenous injections bypass absorption in the GI Tract. Intramuscular or Subcutaneous injections pass through gaps between cells into capillary walls then into general circulation.

Simple Cuboid Epithelium

  • Single layer of cube shaped cells
  • Associated with glands
  • Lines tiny tubes in kidneys (tubules) where urine is created.
  • Endocrine glands: release hormones into bloodstream (inside body).
  • Exocrine glands: release secretions (sweat, saliva, stomach acid) outside the body through ducts.
  • Examples in microscope slides:
    • Thyroid tissue: single layer of cube-shaped cells creating a pocket around the thyroid hormone.
    • Kidney tubules: tubes created by a single layer of cuboid epithelial cells.

Simple Columnar Epithelium

  • Single layer of rectangular/columnar cells
  • Location: stomach through intestines (GI tract)
  • Columnar cells covered in microvilli (folds) that create a hazy "brush border".
  • The microvilli increase surface area for better absorption.
  • Diseases like Crohn's can cause malnutrition issues due to destroyed cells losing surface area for absorption.
  • Lining of the small intestine includes microvilli to absorb nutrients, water, sugars and fats. Unabsorbed food particles move to large intestine, which absorbs more water and salts. Remaining material enters rectum. Lactose intolerance results in lactose accumulating in the small intestine, which.

Pseudostratified Epithelium

  • "Falsely layered" epithelium
  • Cells have irregular shape
  • Appears to be multiple layers but is one layer
  • Key feature: cilia (hair-like extensions)
  • Mainly in the respiratory system: nasal passageways, trachea, upper respiratory tract.
  • Cilia push things up the respiratory passageway, helping to cough out phlegm.
    • Everything in air (dust, smoke) gets trapped in mucus, then swept away by cilia.

Stratified Squamous Epithelium

  • Many layers of flat, pancake-like cells
  • Top layers are the most flat
  • Found in high friction areas: skin, oral cavity, anal area.
  • Two types:
    • Keratinized: dead cells on top, filled with keratin (rigid, waterproof); on the surface of skin, cells lack a nucleus.
    • Non-keratinized: alive cells on top with a nucleus; on moist body surfaces (inside of mouth and throat).

Transitional Epithelium

  • Does not fit naming scheme
  • Found mainly in the bladder, also prostate
  • Cells change shape based on organ state (empty or full bladder).
  • Empty bladder: cells on surface are almost cuboid shaped (domed/bulged).
  • Full bladder: cells get squished, doming disappears, top cells look squamous.

Connective Tissue

  • Connective tissues share a common origin, develop from mesenchyme. Have different degrees of vascularity. Composed of nonliving material called the extracellular matrix.
    *Three classes of connective tissue: Connective tissue proper, fluid connective tissue, and supportive connective tissue.

Connective Tissue Proper

Characterized by a good amount of ground substance in the extracellular matrix

  • Typically has a good amount of ground substance in the extracellular matrix, phagocytes, collagen, and reticular fibers.
  • Widely dispersed throughout the body.
Loose Areolar Connective Tissue
  • Collagen fibers are loosely packed.
  • Areolar = aerated (like Swiss cheese).
  • Contains collagen, elastic, and reticular fibers.
  • Location: EVERYWHERE (under epithelial lining of skin, surrounds nerves, blood vessels, muscles).
Adipose Tissue
  • Fancy word for fat
  • Mainly made of adipocytes (store energy).
  • Two types:
    • White: what is typically seen in microscope slides.
    • Brown: in newborns/infants, metabolically active to create heat. Not found in adults.
  • Looks like soap bubbles.
  • If energy intake > energy burned, extra energy is stored in the cytoplasm of the adipocyte.
  • Once divided, cannot get rid of the adipocyte. Adipocytes shrink, but surgical removal is required for total removal.
  • Visceral fat (around organs) is associated with heart disease and diabetes.
  • Normal to find a little bit fat around kidneys and eyes. Fat on the surface of the skin creates insulation and protection.
Reticular Connective Tissue
  • Found in lymphatic organs (liver, spleen, lymph nodes).
  • Mesh-like reticular fibers create a spider web appearance to the extracellular matrix (good at trapping things).
  • Lymphatic tissues (foreign particles, virions, etc.) get trapped in the spider web, and the white blood cells that are found in these organs get time to come along and gobble it up.

Dense Connective Tissue

Dense Regular Connective Tissue

*Dense means densely packed collagen fibers with not much white space between and allighned collagen run parallel to each other.

  • Densely packed collagen fibers with not much white space.
  • Collagen fibers are all aligned (parallel to each other).
  • Found in areas where resistance to stretching is needed: tendons, ligaments, vocal cords.
Dense Irregular Connective Tissue
  • Dense = densely packed collagen fibers, but fibers run every which direction.
  • Zoomed in super close shows us really densely packed collagen fibers running every which way.
  • Location:
    • Dermis of skin (lower layer).
    • White of the eye. Gives some strength, stability and structure to it.

Fluid Connective Tissue

Liquid extracellular matrix

  • Extracellular matrix is liquid (plasma).
  • Plasma: mostly water (90%), clotting factors, albumin, antibodies, nutrients (sodium, potassium), gases (oxygen, carbon dioxide).
  • Two types: Blood, Lymph.
Blood
  • In blood vessels (arteries, veins, capillaries).
  • Carries things from point A to point B.
  • Two distinct cell types:
    • White blood cells (leukocytes): have very funky shaped nuclei
    • Red blood cells: missing a nucleus.
Lymph
  • Liquid traveling through lymph vessels and lymph nodes.
  • Every time the heart beats a percentage leaks out into the tissues and gets brought back; Some gets pushed into lymphatic vessels, beaten up by white blood cells inside our lymph nodes and our spleen that cleans, cleans our tissue fluids out.
  • Similar to plasma but without the red blood cells.

Supportive Tissue

Supportive connective tissues are meant to give our body shape and structure.
Cartilage : Rigid but somewhat soft (little bit stretchy, a little bit rubbery, and a little bit pillow like).
Bone: Shape, structure and protection.

Cartilage

  • Similar to bone but somewhat soft.
  • Three types: Elastic cartilage, Hyaline cartilage, Fibro cartilage.
Elastic Cartilage
  • E in elastic = ear and epiglottis (main locations).
    • Ear (external): springs back when bent.
    • Epiglottis: flap of elastic cartilage covering the windpipe (closes when swallowing food).
  • Distinguished by coarse elastic fibers throughout the extracellular matrix.
  • Chondrocyte (Cartilage Cell) surrounded by lacuna space.
Hyaline Cartilage
  • Rigid like bone, but a little bit soft and rubbery.
  • Locations:
    • Embryonic skeleton: the skeleton of the embryo is made out of cartilage, and eventually those cartilage bones will turn into real bones as they develop.
    • Growth plate in children.
    • Rib cartilages: connect ribs to sternum.
    • Nose cartilage: rigid but a little wiggly.
    • Moving joints (elbow, knee, shoulder): reduces friction as bones glide across each other.
  • Extracellular matrix has a hazy appearance.
Fibrocartilage
  • Has wispy collagen fibers within the cartilaginous matrix.
  • Like a pillow.
  • Locations:
    • Intervertebral discs of the spine.
    • Meniscus: little pillow on the knee joint that helps with shock absorption.
    • Pubic symphysis: fibrocartilage pad that lets the pelvis open up during childbirth.

Bone

*Bone is obviously our hardest type of connective tissue. Weight of your bone is actually collagen fibers. Fibers get mineralized by calcium and phosphate and other minerals.

  • Hardest type of connective tissue (second to dentin in teeth).
  • Shape, structure, and protection.
  • Has a lot of collagen.
  • Collagen fibers get mineralized by calcium and phosphate (makes them hard).
  • Looks like archery targets or rings on a tree.
  • Osteocytes (bone cells) living in a lacunae (space).
  • Located in the skeleton.

Muscle Tissue

There are three types of muscle tissue: skeletal, smooth and cardiac.
Know the key features.

Skeletal Muscle

  • Only type of voluntary muscle: needs brain to work -> Can repair.
  • Attached to the skeleton.
  • Moves and stabilizes our body.
  • Long and thread-like cells (fibers).
  • Muscle Fiber: Skeletal muscle cell
  • Many nuclei.
  • Myosin and actin proteins create dark and light striping patterns called striations. ->Striated Muscle
  • Example: Shortness of breath and fluid in the lungs can be pneumonia. Flat cells get square as it picks up on a simple barrier

Smooth Muscle

Muscle of hollow Organs

  • Found in all of our hollow organs walls. walls of digestive tract, walls of bladders, walls of blood vessels.
  • Walls open and close tubes and sacs
  • Under involuntary control. Paralysis does not stop normal functions.
  • Brain can tell those organs to to be more or less excited, but they are reflexes.
  • Brain Can tell Stomach what to do
  • Small, slender, spindle shaped (tapered at the ends).
  • One nucleus per cell.
  • Does not have stripes :No Striations No.
  • Good at repair after injury.

Cardiac Muscle

  • Found in the walls of the heart (Involuntary)-> Brain cannot tell heart to stop.
  • Cells are short and branched.
  • One or two nuclei per cell.
    *Has Striations (dark and light bands)
  • Intercalated discs help with coordinated contraction.
  • Little to no ability to repair
    *Long Term damage to Cardiac Muscle, new heart

Nervous Tissue

*In nervous system, unit 9, 10 and 11. 2 main components that assist the neuron. Nervous Tissue allows bodies to functions depending on Internal and External Environment.

Components

Neurons sends and Receives Informaiton, glial cells help assist neurons, supportive cells that assist the neuron in the function. Consist Electrical and chemical signals(neurotransmitters)

  • Found in brain, spinal cord, and nerves.
  • Allows monitoring of internal and external environments and controlling functions in response.
  • Consists of two main types of cells:
    Neurons and glial cells (neuroglial)
  • Neurons: send and receive information.
    Support cells and and send signals of the body.

Glial Cells= Neural Glial Cells

  • The supportive cells (not cell type) that assist the neuron in their function.
    Basic Parts of a neruron

  • Cell Body or Soma:
    Where nuclus is, and all organelles function. The control center.
    Dendrites is where the cell body is and brings neurons.
    Axons transmit the nerve.

  • Cell body (soma): where the nucleus is, plus organelles; control center.

  • Dendrites: branched appendages that receive information and bring it into the neuron (Receptors that bring Information).

  • Axon: takes information away from the neuron to the next target (another neuron, muscle, gland).

Glial Cells Make Cells Work:

  • Neurons are not myelinated.
  • Schwamm Cells help with the nervous system to send cell faster and oligodendrocyte, they create Myelin Sheath to help insulate neuron with layer of fat.
  • ALS MS : Demyelinating diseases where the myelin sheath are destroyed and cannot transfer. This causes a shut down of Neuron Activity.
  • Epididymal: Helps maintain cerebral Spinal Fluid. Helps fluid float around the brain. If Brain Raddles it can get concussion.
  • If an infection occurs in the brain, a barrier with blood is created, a brainworm could result. Makeoglia helps absorb and defeat the organism to prevent infections in brain or spinal taps.
    *Astrocytes surround capillaries to maintain that blood brain barrier that brain has its enviroment with no brainworm infection.
    *If Your brain has an deviation and you dont supply blood it starts to shut off right away.