Tissues Flashcards
Epithelial tissue (and 2 forms)
- Refers to an epithelium that covers a body surface or lines a body cavity.
2 forms as listed below:
- Covering and lining epithelium, which forms the outer layer of the skin, dips into and lines the open cavities of the urogenital, digestive and respiratory systems and covers the walls and organs of the closed ventral body cavity.
Glandular epithelium, which surrounds the glands within the body.
4 characteristics of epithelial tissue
Polarity — All epithelium has an apical surface and a lower attached basal surface that differ in structure and function.
Specialised contacts — Epithelial cells fit close together and form a continuous sheet. They do this with tight junctions and desmosomes.
Supported by connective tissue — All epithelium are supported by connective tissue. The basement membrane reinforces the epithelium and helps to resist stretching and tearing.
Avascular and innervated — The epithelium is avascular, or contains no blood vessels. It is highly innervated, or supplied by nervous fibres. Epithelium has a high ability to regenerate and can reproduce itself as long as it receives adequate nutrition.
Epithelial classification (5 ways)
Single - simple layer of cells
Stratified - two or more stacked cell layers
Squamous cells - flat and scale-like
Cuboidal cells - box like
Columnar cells - tall, column-shaped
A gland is one or more cells that produce and secrete a specific product. (water-based fluid that usually contains proteins) Glands are classified according to two sets of traits — where they secrete their fluids and how many cells they contain:
Endocrine (Internally secreting)
Exocrine (Externally secreting)
Unicellular glands
(One cell type)
Multicellular glands
(More than one cell type)
connective tissue functions (BPIST)
Binding and supporting
Protecting
Insulating
Storing reserve fuel
Transporting substances within the body
Ground substance
clear, colourless, viscous fluid that fills the space between the cells and fibres
Types of fibres
Collagen - fibrous protein that is extremely tough and provides high tensile strength
Elastic - Elastin stretches and recoil
Reticular - Reticular fibres are short, fine collagenous fibres and branch extensively to form a delicate network.
Cyte vs blast
cyte - mature cell: can maintain the health of the matrix; can revert to their active, immature state to repair and regenerate the matrix.
blast - immature cell: Actively proliferating and secreting the ground substance and the fibres characteristic to their particular matrix
Connective tissue (types)
connective tissue proper
bone
cartilage
blood
connective tissue proper
Loose Connective Tissue: Areolar, Adipose, Reticular
Dense Connective Tissue: Dense Regular, Dense Irregular, Elastic
Cartilage
Hyaline Cartilage
Elastic Cartilage
Fibrocartilage
Loose connective tissue (areolar) function (SDHS):
Supporting and binding other tissues
Defending against infection
Holding body fluids
Storing nutrients
Loose connective tissue (areolar) appearance:
- Most widely distributed
- Fibroblast = dominant cell type
- Loose arrangement of fibres
- Lots of ground substance
Adipose tissue (function)
Store Energy (Lipids)
Cushions and insulates the body
Adipose tissue (appearance)
Sparse
Closely packed adipocytes (fat cells)
Accumulates in subcutaneous tissues where it cushions and insulates the body
Reticular connective tissue
Limited to specific areas where it can support immune cells in the lymph nodes, spleen and bone.
Function:
Internal frameworks that can support immune cells
Reticular connective tissue (appearance)
Delicate network of reticular fibres
Hyaline cartilage
(function and appearance)
Function:
Provides strong support while providing pads for shock absorption.
Appearance:
Large number of collagen fibres, its matrix appears transparent or glassy
Chondrocytes
Elastic cartilage (appearance and function)
Function:
Maintain the shape of the structure while allowing flexibility
Skeleton of the external ear and in the epiglottis
Appearance:
Similar to hyaline cartilage but has many more elastic fibres
Chondrocytes
Fibrocartilage (appearance and function)
Function:
Compressible and resists tension.
Found in the intervertebral discs of the bony vertebrae and knee meniscus.
Appearance:
Rows of Chondrocytes alternating with rows of thick collagen fibres
Bone: functions
Supports and protects body structures
Stores calcium and other materials and fat
bone marrow = site for synthesising blood cells
Bone (appearance)
Hard, calcified matrix containing many collagen fibres
Osteocytes, reside in the lacunae
Osteoblasts
Osteons formed of concentric rings of bony matrix (lamellae)
surrounding central canals containing blood vessels and nerves
Blood (appearance and function)
Function:
Delivers necessary substances such as nutrients and oxygen to the cells
transports metabolic waste products away from those same cells.
Appearance:
Red and white blood cells surrounded by a non-living fluid called plasma
Muscle cells (skeletal) function:
attach to bones to enable us to produce voluntary movement
Attach to move bones through contracting and relaxing in response to voluntary messages from the nervous system
Long, cylindrical, multinucleate cells; striated appearance
Muscle cells (smooth) function:
line hollow organs to help squeeze substances through these organs.
Spindle-shaped cells with central nuclei, no striations; cells arranged closely to form cells
Propels substances (food, urine) or objects along internal passageways
Involuntary
Cardiac muscle: function
lines the walls of the heart to propel blood through blood vessels to other parts of the body
Branching, striated, generally uninucleate cells that connect at specialised junctions called intercalated discs.
Found only in the myocardium, it contracts in response to signals from the cardiac conduction system to make the heart beat, and propel blood around the body.
Nervous tissue (structure)
Primary tissue found in the central nervous system and the peripheral nervous system i.e. brain, spinal cord, nerves
Regulate and control body function
Made up of neurons - sense stimuli and transmit nerve impulses around body
Neurons (components)
Cell Body: The central cell body contains the neuron’s nucleus and other organelles.
Nerve Processes: projections from the cell body that are able to conduct and transmit signals.
Axons - carry signals away from the cell body
Dendrites - carry signals toward the cell body
Nervous tissue: Glial cells (functions SASRMNP)
Support nervous system
Astrocytes form blood brain barrier
Supply of nutrients to neurons
Removes excess neurotransmitters
Maintains electrolyte balance
Nervous system repair
Protection against microorganisms
Tissue healing (epithelial vs nervous)
Epithelial tissue e.g. fingers - takes a few days to completely repair
Nervous tissue e.g. spinal cord injuries - can lead to long lasting and permanent impairments
Tissue healing: regeneration
proliferation of cells and tissue. Complete restoration of lost tissue structures.
Tissue healing: repair
proliferation of cells, tissue and scar formation.
Tissue structure will not be restored.
If tissue is incapable of complete restoration or is severely damaged; connective tissue is laid down causing scars , leading to structural rearrangements.
Fibrosis - connective tissue replaces normal tissue; excess connective tissue - tissue remodelling.
Regeneration capacity
Regenerates extremely well. e.g. Epithelial tissue, bone, dense irregular connective tissue, blood-forming tissue.
Moderate Regenerative Capacity e.g. Smooth muscle and dense regular connective tissue
Weak Regenerative Capacity e.g. Skeletal Muscle and Cartilage
Loss of ability to divide after early development and virtually have no functional regeneration capacity - routinely replaced by scar tissue e.g. nervous tissue and cardiac muscle
