Circulatory Components Flashcards
Diffusion
Bulk flow / Convective transport
- pressure gradient
- one way valves
Open vs Closed circulatory system
- Interstitial fluid
- Lymph
Interstitial - Circulating fluid
Lymph - Extracellular fluid of body tissues
Circulatory systems have 3 main components
1+ pumps
System of tubes (vessels), channels, sinuses
Fluid circulating thru system
Contractile chamber (hearts)
External pump (skeletal muscles)
Pulsing/Contractile blood vessels and Tube-like hearts
Invertebrates, vertebrates
Vertebrates
Invertebrates
Circulatory system fluids:
Interstitial fluid
Blood
Lymph
Hemolymph - Hemocoel
Hemocytes
Hemocoel: Body cavities in open circulatory systems
Hemocytes help w/
- O2 transport/storage
- Nutrient transport/storage
- Phagocytosis of damaged cells
- Immune defense
- Blood clotting
Insect hemocytes:
Plasmatocyte - Phagocytosis
Lamellocyte - Fight parasites
Crystal cell - Contain enzymes to lyse invaders
Vertebrates:
Erythrocytes - Red blood cells
Thrombocytes - Platelets
Leukocytes: Lymphocytes (T cells, etc), Monocytes/Macrophages (respond to invaders), Granulocytes (neutrophils, eosinophils, basophils)
Vertebrate blood components:
- Plasma (55%)
- Erythrocytes (45%) - Hematocrit
- Immune cells
- Blood clotting cells
Arteries (arterioles)
Capillaries
Veins (venules)
Carry oxy and deoxy blood
Lack smooth muscle and elastic tissue reinforcement
Contain valves
Lumen:
- Tunica intima
- Tunica media
- Tunica externa
Anastomoses
- Venous shunts
Arteries vs Veins structural diffs
Simple squamus epithelium
Smooth muscle
Connective tissue
(In to out)
Venous shunts: If it’s taking too long to blood clot after injury, pathways constrict to reduce blood loss
Arteries:
- Thicker tunica media, narrower lunens
- More elastic + collagen fibers
Veins:
- Thicker tunica externa, larger lumens and valves
Elastic arteries
Muscular arteries
Arterioles
Pericytes
- Elastin in all 3 tunics
- Large lumen, low resistance
- Inactive in vasoconstriction
- Pressure reservoirs (expand and recoil as blood ejected from heart to smooth pressure)
- Thick tunica media, smooth muscle
- Active in vasoconstriction
- Control flow in capillary beds w/ vasodilation and vasoconstriction
- Stabilize walls and control permeability in capillaries
- Thin tunica intima, only one blood cell thru at a time
Capillary transport mechanisms
1) Diffusion
2) Paraceular pathways
3) Thru fenestrations
4) Transcellular pathways/Transcytosis (vesicles)
- Lipid-soluble substances
Movement thru intercellular clefts
- Water-soluble substances
- Water-soluble substances
- Large substances
Capillary structure types
- Continuous
- Fenestrated
- Sinusoid
- Skin and muscles
- Tight junctions w/ intercellular clefts
- Pores/fenestrations
- Absorption or filtrate formation (in small intestines, endocrine glands, kidneys)
- Large intercellular clefts and lumens
- Sluggish blood flow
- In liver, bone marrow, spleen, adrenal medulla
- Macrophages in lining destroy bacteria
Vasculogenesis
Angiogenesis
Angiogenesis controlled by angiogenic (activator) and angiostatic (inhibitor) molecules
- Normally inhibitor molecules dominant, activator dominant when injured
Angiogenesis mechanism (6 steps)
1) Cells in target sites secrete 1+ angiogenic growth factor
2) Signalling factors bind to receptors in endothelial cells of existing vessels
3) Signal transduction pathway (leading to dissolution of basement membrane of endothelium)
4) Proliferation/Sprouting of endothelium
5) Migration of endothelium (Integrins help sprouting vessels grow)
6) Endothelial cells join together, forming tube of blood vessel
Tumor-induced angiogenesis (3 steps)
- Angiogenic vascular endothelial growth factor (VEGF-A)
- VEGF receptor 2 (VEGFR2)
- Metalloproteinases (MMPs)
- Tip cell
1) Tumor secretes angiogenic vascular endothelial growth factor (VEGF-A) and stimulate VEGF receptor 2 (VEGFR2)
2) Endothelial cells secrete metalloproteinases (MMPs) to degrade basement membrane
3) Endothelial cells form tip cell and coordinate sprouting to tumor
Animals that lack circulatory systems:
Sponges
Cnidaria
Flatworms
Flagellated choanocytes
thru mouth into gastrovascular cavity, down tentacles
Thru mouth into gastrovascular cavity, beating cilia
Annelids - Closed or open system?
Earthworm
Closed
Blood inside pairs of muscular hearts near head w/ connecting vessels; Use peristalsis
Oxy blood -> Heart to body
Deoxy -> Gills to heart
Mollusks - Hearts/Contractile organs
Open circulatory system - Bivalve
Closed circulatory system - Cephalopods
Blood moves thru heart and large vessels
- Mixes w/ interstitial fluid
Oxy blood -> Heart to body
Deoxy -> Gills to heart
Arthropod - Open system + hemolymph
Brachiopod crustaceans
Decapod crustaceans - Ostium
Simple system
- Few blood vessels, long tubular heart
Elaborate open systen
- Chamber-like heart, ostium (small openings) open and close in response to heart relaxation and contraction
Myogenic hearts - Humans
Neurogenic hearts - Decapod crustaceans
- Systole vs diastole
Neurogenic: Contract in response to signals from nervous system
- Systole - Push blood into arteries
- Diastole - Suck blood inside
Insect open circulatory system
Large dorsal vessels, ostia, hemolymph
- Not very involved in O2 transport
Systemic circuits
Fish
Tetrapods (amphibians)
Reptiles
Reptiles (crocodilians) - Foramen of Panizza
Mammals and birds
2 chambers - 1 atrium 1 ventricle
3 chambers - 2 atria 1 ventricle (where blood mixes, reducing oxygenation)
3 chambers - Ventricle divided by partial septum (reduce mixing), 2 main arteries taking blood to lungs and stomach
4 chambers- Hole between 2 ventricles, can also shunt blood from lungs to stomach
4 chambers
