- Connective Tissue (CT) binds to and supports body parts
- Muscle Tissue protects joints, produces movement and heat
- Nervous Tissue responds to stimuli and transmits impulses from one body part to another
- Epithelial Tissue covers body surfaces and lines body cavities
- Skin is an organ
- Epidermis of skin is made of stratified squamous epithelium
- New cells are pushed outward, become keratinized, die and are rubbed off
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Classification of Epithelium |
- Simple epithelium: Composed of a single cell layer
- Found in the alveolar (air sacs) wall of the lung
- Increases rate of diffusion by increasing surface area and reducing diffusion pathway
- Stratified epithelium: Composed of multiple cell layers
- Squamous: Cells have a flattened appearance, with a flattened nucleus
- Cuboidal: Cells appear as a cube, the nucleus is spherical
- Columnar: Cells are column shaped with an elongated nucleus
- Cilia: Small projections that can move small substances
- Lines the respiratory tract
- Cleans impurities by moving them upwards, towards the throat
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| Blood is a connective tissue containing different cell types (erythrocytes, lymphocytes, monocytes, granulocytes) |
Blood Plasma |
- Plasma is aq containing proteins, inorganic salts, amino acids, vitamins, hormones
- Main plasma proteins are albumin, globulins, and fibrinogen
- Albumin maintains osmotic pressure and acts as a transport protein for various substances
- Globulins are mainly antibodies
- Fibrinogen is involved in clotting process
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Erythrocytes
(red blood cells) are filled with O2 carrying haemoglobin |
- Contain the respiratory pigment haemoglobin which carries oxygen
- Biconcave discs 7.5 µm in diameter
- Biconcave shape provides large surface-to-volume ratio for O2 delivery
- Also allows greater flexibility in thin capillaries
- Maturation in bone marrow takes 24-48h
- Loose mitochondria, nucleus,… during maturation for O2 carrying
- \ No aerobic respiration possible → depends on anaerobic respiration
- Proteins serve as acid-base buffers //anaerobic respiration produces lactic acid
- Survive in circulation for ≈120 days
- Old cells are removed by phagocytic cells of spleen and bone marrow
- Decrease of red blood cells is called anaemia
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Leukocytes (white blood cells) |
- Involved in cellular and humoral defence of organism
- [MECHANISM] Leave circulatory system to enter tissues
- Margination: Leukocytes flow in plasmatic zone (next to the tunica intima)
- Adhesion: They randomly contact or "roll over" the endothelium
- Emigration: Migration through the wall of venules and small veins
- Diapedesis: Passive escape of red cells from vessels
- Classified into granulocytes and agranulocytes
- Based on the presence or absence of visible granules within the cellular cytoplasm
- Granulocytes / presence of granules / neutrophils, eosinophils, and basophils
- Agranulocytes / absence of granules / monocytes and lymphocytes
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Lymphocytes (6-18µm)
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 image taken from http://www.crnasomeday.com/anatpages/theblood.php |
- Spherical nucleus and shape, very little cytoplasm
- Memory cells have specific antigen receptors on the cell surface
- Lymphocytes vary in life span. Some live few days, others many years
- Only white blood cells that return to blood stream after migrating to tissues
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Monocytes (12-20µm) |
 image taken from http://www.crnasomeday.com/anatpages/theblood.php |
- Oval, horseshoe or kidney shaped nucleus; more cytoplasm than lymphocytes
- Nucleus does not stain as darkly as lymphocytes in blood smears
- After leaving circulatory system, they differentiate into macrophages in connective tissues
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Granulocytes |
- Lobed nucleus and granular cytoplasm
- Different functions: some engulf bacteria; others are involved with allergies and inflammation
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Blood vessels |
| Arteries |
- Pulmonary artery
- Transport deoxygenated blood from the right ventricle into lungs
- Systemic arteries
- Transport oxygenated blood from left ventricle to body tissues
- About 10% of total blood volume is in systemic arterial system at any given time
- Blood is pumped from the left ventricle into large elastic arteries
- Elastic arteries become smaller muscular arteries
- Muscular arteries branch into smaller arterioles (smallest arteries)
- Arterioles regulate blood flow into tissue capillaries
- Arterial wall consists of 3 layers:
- Innermost layer, tunica intima, is simple squamous epithelium / surrounded by a connective tissue basement membrane with elastic fibres
- Middle layer, tunica media, is smooth muscle and usually thickest layer / changes vessel diameter to regulate blood flow and blood pressure
- Outermost layer, tunica adventitia, attaches vessel to surrounding tissue / connective tissue with varying amounts of elastic and collagenous fibers
- Arteries have a relatively small lumen (compared to veins)
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Veins |
- Pulmonary veins
- Transport oxygenated blood from lungs to left atrium
- Systemic veins
- Carry deoxygenated blood towards the heart
- After blood has passed through the capillaries, it runs into venules (smallest veins)
- Afterwards, veins become progressively larger until they reach the heart (right atrium)
- Medium and large veins have valves that help to keep blood flowing toward heart
- This is important in arms and legs to prevent backflow of blood due to gravity
- Walls of veins have same three layers as arteries
- BUT less smooth muscle and connective tissue
- Makes walls of veins thinner with less pressure → Larger lumen
- Can hold more blood than arteries
- Almost 70% of total blood volume is in veins at any given time
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