Respiratory system and circulation Flashcards
(56 cards)
What is arterial system?
Aorta –> arteries –> arterioles –> branch into capillaries
What is venus system?
Capillaries –> diverge into venues –> veins –> vena cava
Which vessels act as volume reservoir?
Veins.
They can send blood back to arteries if blood pressure suddenly drops.
Which vessels act as pressure reservoir?
Arteries with their thick elastic walls which contract according to cell rhythm.
Which vessels act as the site of variable resistance (may change blood flow to the tissues)?
Arterioles.
They may selectively constrict and dilate according to paracrine signals.
What are metarterioles?
The type of arterioles just before capillaries.
There are precapilary sphincters between metaarterioles and capillaries to restrict blood flow to certain capillaries according to some signals.
Metaarterioles may also act as bypass channels: connect arterioles and venules without entering capillaries.
Which layer of vessels sends paracrine signals?
Endothelium secrets paracrine signals.
What are the basic layers of vessels and their functions?
1) Endothelium (inner lininng): sends paracrine signals, allows transport of nutrients with its leakiness in capillaries.
2) Elastic tissue: connective tissue for elasticity (ability to stretch and retain back to its original shape).
3) Smooth muscle in circular or spiral layers: always partially contracted (have muscle tone) according to hormones and neurotransmitters. Contraction depends on Ca2+ entry.
4) Fibrous tissue: connective tissue for vessel stiffness (prevent it from damage due to pressure).
What are the structural features of the arteries?
- From 0.1 mm to over 1 cm in diameter
- Walls are 1 mm thick
- have lots of smooth muscle (the most among other vessel types)
- have slightly less elastic tissue (still the most among other vessel types)
- have some fibrous tissue (the same amount as in venules and veins)
What are the structural features of arterioles?
- 10-100 microns in diameter
- Walls are 6 microns thic
- have some smooth muscle (the same amount as in veins)
- have no elastic and fibrous tissue
What are the structural features of capillaries?
- 4-10 microns in diameter
- 0.5 microns thick
- have one-cell thick endothelium only (no muscle, no elastic and fibrous tissue)
- endothelium is leaky, there are pores between cells allowing blood plasma to enter extracellular fluid
- contractive pericytes (irregularly shapes highly branched cells) surround capillaries and control their level of leakiness
- capillaries are supported with basal lamina
What are the features of venules?
- 10-100 microns in diameter (just like arterioles)
- walls are 1 micron thick (6 time thinner than in arterioles)
- have some fibrous tissue (the same amount as in arteries and veins)
- have no muscle tissue and elastic tissue
What are the structural features of veins?
- from 0.1 mm to 1.5 cm in diameter
- walls are 0.5 mm thick
- have some muscle tissue (the same amount as in arterioles)
- have some elastic and fibrous tissue in the approximately equal amount
What are other differences between veins and arteries?
Veins:
- located closer to the body surface, they are visible under skin
- there more veins than arteries
- some have valves to prevent blood backflow
- skeletal muscles contraction helps to pump venous blood back to the heart
Arteries:
- found deeper in body, far away from the body surface
- no valves
- only rely on the heart for blood pumping
What is external respiration?
Movement of gases (particularly oxygen and carbon dioxide) between the environment and body cells.
There are 3 stages:
1) ventilation: air to lungs (airways and alveoli)
2) lugs to blood (pulmonary and systemic circulation)
3) blood to cells
What is upper respiratory tract?
1a) oral cavity
1b) nasal cavity
2b) pharynx
3) larynx
What is lower (thoracic) respiratory tract?
1) trachea
2) two primary bronchi
3) secondary (lobar) bronchi
4) teriary (segmental) bronchi
5) bronchioles, surrounded with smooth muscle (like arterioles, they can constrict and dilate)
6) alveoli cluster on the end of bronchioles. Surrounded by the dence network of elastic fibres (elastin and collagen) and capillaries.
Starting from the middle of primary bronchi, the rest are inside of lungs.
Trachea and bronchi are covered with ring cartilage to prevent collapse. They are not fully closed to allow enough expansion.
What is the function of pleural membranes and pleural fluid between them?
- Decease friction when lungs expand in thorax
- Hold lungs tight against the thoracic wall
What can disrupt the normal function of pleural membranes?
Pleurisy: inflammation of pleural membranes due to infections. Makes breathing difficult because friction increases.
Pleural effusion: accumulation of pleural fluid, creates pressure to decrease normal lung volume.
Pneumothorax: normal pressure in pleural space is subatmospheric (-3 mm Hg); but when pleural membranes are damaged (often due to knife stubbed into chest), pressure becomes equal to atmospheric and lung collapses.
What are the features of the surface tissue in the airways?
- columnar ciliated epithelia with tight junctions
- covered with mucus and saline, which are produced by submucosal glands and goblet cells
- mucus traps dirt and pathogens, cillia beat to remove mucus away from the airways
- saline layer decreases friction when mucus is removed away with cillia beating
What are the cells in alveoli?
Type I: gas exchange
- one cell thick layer of squamous epithelia (thin cells to allow faster gas diffusion)
Type II: surfactant production:
- prevent alveoli collapse by decreasing surface tension
- killing pathogens
- regulate other immune responses
There are also alveolar macrophages to keep alveoli clean.
What is the difference between active (forced) and passive (quiet) breathing?
Passive: normal breathing, diagram takes most of the load among muscles.
Active: deep breathing, often after physical activity or voluntary control. Several muscles are involved: diaphragm, interconstals etc.
