Human Tissue Histology Part 1 Organization of the

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Human Tissue & Histology Part 1: Organization of the Human Body

Human Tissue & Histology Part 1: Organization of the Human Body

Tissue n n Tissue: A group of similar cells (and cell products) that arise

Tissue n n Tissue: A group of similar cells (and cell products) that arise from the same region of the developing human embryo and work together to perform a specific task. Primary Germ Layers are the rapidly dividing cells of a zygote organized into 3 layers that form epithelial tissue: ¨ Endoderm: The innermost germ layer; develops into parts of the digestive and respiratory system. ¨ Mesoderm: The middle germ layer; develops into bone, muscle, and connective tissue. ¨ Ectoderm: The outermost germ layer; develops into epithelium and nervous tissue

Types of Tissue n Four basic types of tissue: ¨ Epithelial: Covers surfaces or

Types of Tissue n Four basic types of tissue: ¨ Epithelial: Covers surfaces or lining tubes and hollow organs in the body, also forms glands ¨ Connective: Provides support, protection, and fills spaces. n Helps bind organs together; Stores energy reserves; Useful in providing immunity ¨ Muscular: When stimulated by nerve impulses, produces movement. ¨ Nervous: Neurons initiate nerve impulses. n Neuroglia provide support to neurons.

Epithelial Tissue n Epithelium: Cells tightly arranged in continuous sheets with little intracellular space.

Epithelial Tissue n Epithelium: Cells tightly arranged in continuous sheets with little intracellular space. ¨ Form boundaries between the body’s organs or protects the body from the external environment ¨ High rate of cell division helps keep the tissue in constant repair n TWO primary categories: Covering & Lining Epithelium n Glandular Epithelium n

Covering & Lining Epithelium Forms the outer covering of skin and some organs n

Covering & Lining Epithelium Forms the outer covering of skin and some organs n Forms the lining of blood vessels, ducts, and body cavities n Lines the interior of most of the body’s systems (respiratory, digestive, reproductive, etc. ) n Further subdivided by layer and cell type. n

Covering & Lining Epithelium: Layers n 3 Layers: ¨ Simple: A single layer of

Covering & Lining Epithelium: Layers n 3 Layers: ¨ Simple: A single layer of cells that functions in diffusion, osmosis, filtration, secretion, and absorption ¨ Stratified: Composed of two or more layers of cells that protect underlying tissues in locations where there is considerable wear and tear. ¨ Pseudostratified: Contains a single layer of cells; not all cells reach the apical surface and are either ciliated or secrete mucous

Covering & Lining Epithelium: Cell Shapes n Cell Shapes: ¨ Squamous: Thin and tile-like

Covering & Lining Epithelium: Cell Shapes n Cell Shapes: ¨ Squamous: Thin and tile-like ¨ Cuboidal: Cube shaped. ¨ Columnar: Column shaped ¨ Transitional: Change shape

Covering & Lining Epithelium in the Human Body n Simple Squamous Epithelium: Lines the

Covering & Lining Epithelium in the Human Body n Simple Squamous Epithelium: Lines the heart and blood vessels (endothelium), air sacks of the lungs, and serous membranes (mesothelium)

Covering & Lining Epithelium in the Human Body n Simple Cuboidal Epithelium: Used primarily

Covering & Lining Epithelium in the Human Body n Simple Cuboidal Epithelium: Used primarily in secretion and absorption

Covering & Lining Epithelium in the Human Body n Simple Columnar Epithelium: Found in

Covering & Lining Epithelium in the Human Body n Simple Columnar Epithelium: Found in the lining of the gastrointestinal tract (nonciliated) and respiratory tract (ciliated)

Covering & Lining Epithelium in the Human Body n Stratified Squamous Epithelium: Lines wet

Covering & Lining Epithelium in the Human Body n Stratified Squamous Epithelium: Lines wet surfaces like mouth, epiglottis and vagina (non-Keratinized); superficial skin layer (Keratinized), ureters, and urethra.

Covering & Lining Epithelium in the Human Body n Transitional Epithelium: Lines urinary bladder

Covering & Lining Epithelium in the Human Body n Transitional Epithelium: Lines urinary bladder to permit distension

Glandular Epithelium n Glandular Epithelium: The primary function is sectretion. ¨ Gland: Any collection

Glandular Epithelium n Glandular Epithelium: The primary function is sectretion. ¨ Gland: Any collection of cells that secrete substances either into the blood, onto the surface, or into the ducts. Two major categories: Endocrine and Exocrine

Endocrine Glands: Secrete hormones directly into the bloodstream to regulate body activities. n Examples:

Endocrine Glands: Secrete hormones directly into the bloodstream to regulate body activities. n Examples: n ¨ Pituitary Gland ¨ Adrenal Gland ¨ Thyroid Gland

Exocrine Glands n n n Exocrine Glands: Secrete various materials such as mucous, saliva,

Exocrine Glands n n n Exocrine Glands: Secrete various materials such as mucous, saliva, and sweat into ducts that then empty onto the surface of a covering or lining epithelium. Two major categories: Unicellular (like goblet cells) or Multicellular (like sebaceous or oil glands) Means of Secretion: Merocrine Glands: Use exocytosis to secrete materials from cells and release secretions synthesized by ribosomes. Ex. Salivary pancreatic glands. ¨ Apocrine Glands: Accumulate secretions on the surface of the cell which are then “pinched off”. Ex. Mammary glands ¨ Holocrine Glands: Accumulate secretions in the cytosol until the entire cell ruptures to release it. Ex. Sebaceous glands on skin. ¨

Epithelial Membranes n Epithelial Membrane: Combination of an epithelial layer and an underlying connective

Epithelial Membranes n Epithelial Membrane: Combination of an epithelial layer and an underlying connective tissue layer. 3 Main Types: ¨ Mucous Membranes (Mucosa): Lining of the body cavities that open to the outside of the body. n E. g. lining of the entire digestive, respiratory, and reproductive tracts. ¨ Serous Membranes (Serosa): Cover the organs & the cavities that contain them ¨ Cutaneuous Membranes: Skin! n Synovial Membranes: Lines the cavities of movable joints, secreting a fluid that lubricates the cartilage covering the bones at such joints.

Connective Tissue n Connective Tissue: Supports, strengthens, and binds together the other tissues. ¨

Connective Tissue n Connective Tissue: Supports, strengthens, and binds together the other tissues. ¨ Primary site of stored energy (adipose tissue) and immune response ¨ Provides the body its main transport system (blood) ¨ Often has a rich blood supply (with some exceptions) and generally consists of few cells scattered throughout an intercellular matrix or protein fibers and a ground substance which binds the cell together.

Connective Tissue Connective tissue arises from embryonic cells whose name ends in –blast and

Connective Tissue Connective tissue arises from embryonic cells whose name ends in –blast and –cyte n BLAST cells have a high capacty for cell division and are responsible for making the matrix n Once the matrix is formed, the blast cells mature into CYTE cells designed to maintain the matrix. n

6 Types of Connective Tissue n 6 Types of Connective Tissue: ¨ Fibroblasts ¨

6 Types of Connective Tissue n 6 Types of Connective Tissue: ¨ Fibroblasts ¨ Macrophages ¨ Plasma Cells ¨ Mast Cells ¨ Adipocytes ¨ White Blood Cells

6 Categories of Mature Connective Tissue 1. Loose Connective Tissue: Most common type found

6 Categories of Mature Connective Tissue 1. Loose Connective Tissue: Most common type found in the human body. Composed of areolar, adipose, and reticular tissues. Many cells present and fibers loosely intertwined. 1. 2. 3. Areolar: Forms subcutaneous layer that attaches skin to underlying tissues. Adipose: Stores triglycerides (fat). Provides insulation and a source of energy reserves. Reticular: Forms the supporting framework of the liver, lymph nodes, and spleen and binds smooth muscle cells together.

6 Categories of Mature Connective Tissue 2. Dense Connective Tissue: Has thicker fibers and

6 Categories of Mature Connective Tissue 2. Dense Connective Tissue: Has thicker fibers and fewer cells than loose tissue. Due to toughness and pliability, forms tendons and ligaments, providing strong points of attachment. Subdivided into 3 kinds: 1. 2. 3. Dense Regular Connective Tissue: Tissue is tough, silvery -white and pliable – forms ligaments and tendons; contains regularly arranged bundles of collagen fibers Dense Irregular Connective Tissue: Occurs where forces pull from multiple directions; forms pericardium around the heart; heart valves and the dermis of skin; contains closely collagen fibers, irregularly arranged. Elastic Connective Tissue: Easily resumes normal shape after being stretched – makes up lung tissue and walls of elastic arteries; contains branching elastic fibers.

6 Categories of Mature Connective Tissue 3. Cartilage: Made up of tightly packed collagen

6 Categories of Mature Connective Tissue 3. Cartilage: Made up of tightly packed collagen and elastic fibers in a rubbery substance known as chondroitin sulfate. Provides support for ears, nose, and trachea, intervertebral disks; makes up the embryonic skeleton. 3 Types of Cartilage: 1. 2. 3. Hyaline Cartilage: Most abundant and weakest type in human body; provides smooth surface for movement at joints; located at articular cartilage & epiphyseal plates. Fibrocartilage: Exists at kneecaps and the discs between the vertebrae to provide support & connectivity; strongest type. Elastic Cartilage: Gives shape and support; found in epiglottis and external ear; provides strength and elasticity.

n n Hyaline Fibrocartilage n Elastic

n n Hyaline Fibrocartilage n Elastic

6 Categories of Mature Connective Tissue 4. Bone Tissue: Known as osseous tissue; composed

6 Categories of Mature Connective Tissue 4. Bone Tissue: Known as osseous tissue; composed primarily of collagen and calcium phosphate (provides durability); divides into two categories: 1. Compact Bone: Composed of osteons 2. Spongy Bone: Lacks osteons

n Compact Bone n Spongy Bone

n Compact Bone n Spongy Bone

6 Categories of Mature Connective Tissue 5. Blood Tissue: Liquid matrix is blood plasma

6 Categories of Mature Connective Tissue 5. Blood Tissue: Liquid matrix is blood plasma with formed elements suspended in it.

6 Categories of Mature Connective Tissue 6. Lymph: Extracellular fluid flowing in lymphatic vessels.

6 Categories of Mature Connective Tissue 6. Lymph: Extracellular fluid flowing in lymphatic vessels. Serves a variety of functions.

Muscle Tissue n Muscle Tissue: Consists of muscle fibers that use ATP to generate

Muscle Tissue n Muscle Tissue: Consists of muscle fibers that use ATP to generate movement & heat. 3 classifications: Skeletal Muscle Tissue: Striated tissue attaches to bones of the skeleton, usually by tendons, & is used to produce movement & heat. Under voluntary control. ¨ Cardiac Muscle Tissue: Forms most of the heart wall & tissue; responsible for pumping blood; under involuntary control. ¨ n ¨ Cardiac muscle cells are branched & attach to each other by thick circles of plasma membrane known as intercalculated discs Smooth Muscle Tissue: Spindle-shaped fibers; under involuntary control; found along the hallow internal structures, mainly blood vessels, intestines, stomach, uterus, airways, etc. Primarily responsible for moving materials through these structures.

n n Skeletal n Smooth Cardiac

n n Skeletal n Smooth Cardiac

Nervous Tissue n Nervous Tissue: Senses stimuli & converts them into nerve impulses or

Nervous Tissue n Nervous Tissue: Senses stimuli & converts them into nerve impulses or signals to different parts of the human body. Two kinds of nerve cells: ¨ Neuron ¨ Neuroglia

Neuron n n Neuron: AKA Nerve cell; responsible for converting stimuli into impulses. Impulses

Neuron n n Neuron: AKA Nerve cell; responsible for converting stimuli into impulses. Impulses travel only one direction along the cell. Made up of 3 Major Parts: Cell Body: Contains the nucleus and organelles ¨ Dendrites: Multiple branched tapering projections that receive impulses from other cells and move up toward the cell body. ¨ Axon: Single, cylindrical projection that carries the signals away from the cell body and to the next neuron or other tissue. ¨ n Nerve impulse always moves from the receiving dendrite, through the cell body, and out the axon to the axon terminals, synapse, and the next dendrite.

Neuroglia: AKA Glia. Comprise about half of the central nervous system & serve a

Neuroglia: AKA Glia. Comprise about half of the central nervous system & serve a variety of important roles. n More on these later! n

Cell Junctions: Places where cells anchor to one another to form seals; some form

Cell Junctions: Places where cells anchor to one another to form seals; some form channels that allow molecules & ions to pass from cell to cell. n 5 Primary Types of Cell Junctions: n ¨ Adherens Junctions ¨ Desmonomes ¨ Gap Junctions ¨ Hemidesmosomes ¨ Tight Junction

Adherens Junctions n Adherens Junctions: Contain proteins on the inside of the cell membrane

Adherens Junctions n Adherens Junctions: Contain proteins on the inside of the cell membrane called plaque. ¨ Provides a strong attachment between adjacent cells by means of cadherins (glycoproteins which bind together to anchor cells next to each other).

Desmosomes n Desmosomes: Like adherens junctions, they provide a means of holding two cells

Desmosomes n Desmosomes: Like adherens junctions, they provide a means of holding two cells tightly together ¨ Use keratin filaments ¨ Found in the epidermis (outer layer of the skin) & between cardiac muscle cells

Gap Junctions n Gap Junctions: Create intercellular channels that permit passage of small molecules

Gap Junctions n Gap Junctions: Create intercellular channels that permit passage of small molecules & ions from one cell to another. ¨ Essential for the spread of nerve & muscle impulses ¨ In cardiac muscle & smooth muscle of the GI tract as well as some synapses in the brain

Hemidesmosomes n Hemidesmosomes: Resemble desmosomes, though their primary responsibility is to anchor other cells

Hemidesmosomes n Hemidesmosomes: Resemble desmosomes, though their primary responsibility is to anchor other cells to the basement membrane (the extracellular layer between epithelium & connective tissue).

Tight Junctions n Tight Junctions: Strands of proteins that fuse cell membranes together, thus

Tight Junctions n Tight Junctions: Strands of proteins that fuse cell membranes together, thus controlling the passage of molecules & ions through the space in between cells. ¨ Found in the lungs & tissues lining the stomach, intestines, and urinary bladder.

Tissue Repair n Tissue Repair: The process by which damaged, worn, or dead cells

Tissue Repair n Tissue Repair: The process by which damaged, worn, or dead cells are replaced. The rate & capacity for repairing damaged cells varies with the kind of tissue. ¨ Epithelial Tissue: Undergoes lots of wear & tear and often has a high capacity for self-repair. n Stem Cells: Immature, undifferentiated cells that can divide to replace damaged cells. Sometimes mature, undifferentiated cells can divide to do the same. ¨ Connective Tissue: Capacity for renewal depends a large part on the blood supply. Bone, for example, renews cells easily, whereas cartilage does not. ¨ Muscle & Nervous Tissue: Have poor capacity for repair, mainly due t the lack of stem cells available.

Tissue Repair n Two primary types of tissue repair: ¨ Regeneration: Injured tissue is

Tissue Repair n Two primary types of tissue repair: ¨ Regeneration: Injured tissue is replaced through cell division of the same type of cells (known as parenchyma). ¨ Fibrosis: Fibroblasts synthesize collagen & other materials to form scar tissue. n If damage is extensive, both processes take place to create a growing connective tissue called granulation tissue which forms the stroma (framework) for new cells to move in & protects against bacteria.

Ailments That Prompt Tissue Repair n Cellulitis: A bacterial infection of the skin &

Ailments That Prompt Tissue Repair n Cellulitis: A bacterial infection of the skin & underlying tissues.

Ailments That Prompt Tissue Repair n Abscesses: Inflamed infection of tissues as a result

Ailments That Prompt Tissue Repair n Abscesses: Inflamed infection of tissues as a result of pus accumulation.

Ailments That Prompt Tissue Repair n Ulcers: Open sores that result when inflamed tissue

Ailments That Prompt Tissue Repair n Ulcers: Open sores that result when inflamed tissue sloughs off from the surface of an organ.