Types of biological tissues Flashcards
What are the four types of biological tissues?
Epithelial
Connective
Muscle
Nervous
What are the two types of epithelial tissue?
Proper and glandular epithelium
Briefly describe proper epithelium
It covers and lines the inner and outer body
Briefly describe glandular epithelium
It forms glands and secretes hormones, as well as other substances
Where is epithelial tissue found?
- Interface between compartments
- Line / cover all body surfaces, cavities and tubes
- Glands
Name three functions of epithelium
- Covering, lining and protecting surfaces
- Performing absorption
- Secretion
What are the characteristics of epithelia?
–Specialised cell to cell junctions
–Polarised
–Basement membrane
–Avascular– rely on connective tissue
What are the three types of epithelium cell types?
Squamous
Cuboidal
Columnar
Squamous epithelium
Lining and diffusion •Endothelium •Blood vessels and lymph •Mesothelium •Body cavities linings
Columnar epithelium
Much more active
What are the three types of layers of epithelium?
Simple- one layer of cells
Stratified- multiple layers on top of each other
Pseudostratified- mostly just one layer. Cells with different shapes and sizes
What is transitional epithelium?
Stratified epithelium that can accommodate stretching
Type of epithelium required for selective diffusion?
These epithelia are usually simple squamous type, to provide the smallest barrier to diffusion.
Type of epithelium required for absorption/secretion?
These epithelia are usually columnar, as the cells contain lots of ER and golgi, for secretion. They often have microvilli, to increase the surface area of the apical surface for absorption.
Type of epithelium required for physical protection?
These epithelia are always stratified (many layers), and can sometimes be keratinised on its apical surface, as in skin. The keratin helps to waterproof the skin.
Where do endocrine glands secrete into?
They secrete hormones into the blood or to nearby cells
Where do exocrine glands secrete into?
They secrete into tubes/ducts that lead to the outside of the body
What can secretory cells synthesise, store and release?
- Proteins-e.g. in the pancreas
- Lipids-e.g. adrenal, sebaceous glands
- Complex of carbohydrates and proteins-e.g. salivary glands
- All the above-e.g. lactating mammary glands
Name the four types of connective tissue
Proper
Cartilage
Bone
Blood
How is connective tissue different to the other types of tissue?
Connective tissue is manly constituted of extracellular matrix rather than cells.
What are the three main components of connective tissue?
Three types of fibres (collagen, elastic, reticular)
Ground substance
Main featured cells
Collagen fibres
Makes up 30% of the human body’s dry weight
At least 28 types exist in vertebrates.
Created by mainly fibroblast cells
It’s what gelatin is made out of
Elastic fibres
Have a rubber-like quality
Made out of the protein Elastin
Found in skin, lungs and large blood vessel walls
Reticular fibres
Also made of collagen
Found in long bones and immune tissue
Suspends growing erythrocytes and plasma cells from its network i.e. bone marrow, the spleen, lymph nodes
Therefore is supportive to areas with rapidly changing populations of proliferating cells
What is ground substance?
Background around fibres and cells are located. The ‘ground substance’ of extracellular matrix is an amorphous gelatinous material. It is transparent, colourless, and fills the spaces between fibres and cells
What does ground substance do?
These molecules are very good at absorbing water, rather like a sponge, such that 90% of the extracellular matrix is made up of water. Allows tissue to return to original shape when compressed or deformed.
Name five types of cells in the extra-cellular matrix
Fibroblasts Macrophages Adipocytes Mast cells Stem cells
Briefly describe fibroblasts
Fibroblasts secrete collagen and elastin. They are the least specialised of the connective tissue cells and can differentiate into other cell types found in the ECM.
Fibroblasts are spindle shaped, and actively secreting matrix.
Briefly describe macrophages
These are phagocytes -these cells ‘eat’ particles such as bacteria. These cells are derived from white blood cells called monocytes
Briefly describe adipocytes
Adipocytes are fat cells. There are two types of fat cells: White Fat Cells, which are the most common type in adults. These are unilocular, have a large diameter, and are found in subcutaneous, omentum & mesentry regions. Brown Fat Cells are multilocular. They are smaller than white adipocytes. They are present in large amounts in the new-born & hibernating animals.
Briefly describe mast cells
They are found close to small blood vessels in loose connective tissue. They contain large secretory granules of heparin proteoglycan-a weak anticoagulant. They also contain histamine, which promotes an inflammatory reaction when secreted
Name the two subdvisions of connective tissue proper
Loose
Dense (regular/irregular)
Briefly describe loose connective tissue
Little collagen
Lots of ground substance
Viscous and gel-like
Inflammatory and immune reactions
Briefly describe dense regular connective tissue
Ordered Densely packed Little ECM Parallel Maximum Strength
Briefly describe dense irregular connective tissue
Mostly collagen Cells are sparse Fibroblast Strength Resistance to tearing and stretching
Bone and cartilage are examples of what type of connective tissue?
Supporting connective tissue
What are the three types of cartilage?
Hyaline: Most common -has a glassy appearance. Sparse collagen.
Fibrocartilage: tendon insertions and invertebral discs: reinforced with parallel bundles of collagen fibres. The strongest.
Elastic cartilage: external ear and epiglottis: flexible and resilient -has elastic fibres as well as collagen fibres.
What are the four main qualities of muscle tissue?
Excitability-the ability to respond to stimuli
Contractibility-the ability to contract-i.e. shorten
Extensibility –the ability to stretch without tearing
Elasticity-ability to return to original shape
Name the three types of muscle tissue
Smooth muscle
Cardiac muscle
Skeletal muscle
Describe smooth muscle tissue
Smooth muscle is unstriated, made of small fusiform cells closely packed together.
Single nuclei that is centrally located.
Found in the walls of hollow organs so sometimes known as visceral muscle.
Under autonomic control
Describe cardiac muscle tissue
Cardiac muscle is striated due to dense arrangements on actin and myosin, and is cylindrical
It is autonomic control.
It has a unique cell to cell junction known as intercalated disks
Single nuclei, based in the centre.
Describe skeletal muscle tissue
Skeletal muscle is a striated, cylindrical muscle under staining due to the dense arrangement of actin and myosin
Each sketetal muscle cell is multinucleated due to being so large, pushed to the periphery
It is under voluntary control –by general somatic efferent
It attaches to bones via tendons, muscles have to traverse a joint in order to have any action.
What are contractions caused by?
Interactions between myofilaments
Give the steps required for contraction
Contraction requires ATP and calcium
Sarcoplasmic reticulum stores calcium
Action potential opens the calcium channels –calcium floods into the cell
Calcium binds with troponin
Deforms tropomyosin, meaning the myosin heads can bind to the newly revealed sites on troponin
ATP –> ADP and P –releases energy
Myosin head binds to actin
What causes contraction to stop?
Calcium stops flooding the muscle fibre because the nerve impulse has stopped. This leads to calcium being depleted. Calcium also unbinds from troponin
Define the term ‘neuron’
Nerve cells that are specialised cells that conduct electrical impulses.
Describe the basic structure of all neurons
Each neuron contains a nerve cell body. Branching off the nerve cell body are the dendrites, which act like tiny antennae picking up signals from other cells. At the opposite end of the nerve cell body is the axon. The axon is insulated by a myelin sheath.
How do nerve impulses travel through neurons?
Nerve impulses are received by the dendrites, travel down the branches of the dendrites to the nerve cell body, and are carried along the axon.
What is the ground substance in blood?
Blood plasma
