B3.2 transport (year 6) Flashcards
Adaptations of capillaries
- large surface area due to branching (capillary beds)
- narrow diameters, one cell thick walls for faster exchange
- fenestrations (small slits that allow relatively large moleules to exit/enter) in some parts where exchange needs to be particularly rapid.
Structure+adaptations of arteries
Receives blood from heart and takes blood to capillary bed
- lined with a thick layer of smooth muscle and elastic fibre, smaller lumen than veins to withstand higher pressures
Adaptations:
- thick layer of smooth muscle is controlled by Autonomic Nervous System (ANS) unconsciously to help regulate blood pressure
- walls of each atery contain elastin and collagen to withstand high pressures.
- once blood surge has passed the elastic fibres recoil and provide further pressure, propeling the blood further forward.
Structure+adaptations of veins
Receives blood from capillary bed and takes blood to heart
- relatively thin-walled with large lumen as lower blood pressure
Adaptations:
- as blood is slow-moving, there are internal valves to prevent backflow of blood.
- thin walls are easily compressed by surrounding muscles.
Describe the occlusion of coronary arteries
Coronary arteries supply blood to cardiac (heart) muscles
- Over time there is a buildup of cholesterol and plaque = restricting blood flow, causing an OCCLUSION
- if an occluded artery is a coronary artery, there is risk of a heart attack as the heart is deprived of oxygen
Adaptations of xylem for transport of water
- lack of cell contents
- imcomplete/absent end walls for unimpeded flow
- lignified walls to withstand tensions created by transpiration and provides resistance to the collapse of the tubes.
- pits (microscopic holes) for easy entry and exit of water when needed
Name + function of the structures in a dicotyledonous stem/root
Epidermis:
STEM: prevents water loss and protection against microorganisms
ROOT: grows root hairs that increase SA/V for more water uptake
Cortex - unspecalized cell layer, sometimes stores food reserves
Vascular bundle - Contains multiple vessels of xylem(inside) /phloem (outside)
Phloem - Transports carbohydrates usually from leaves to other parts
Xylem - transport tubes that bring water usually from roots to other parts
Practice drawing a dicotyledonous stem/root
Pearson pg 316/317
Describe the release and uptake of tissue fluid in capillaries
Tissue fluid is the fluid between cells and blood that allows for the exchange of substances
- constantly renewed by the release from the side of capillary bed closed to the arteriole
- arteriole is the smallest of arteries and branches directly to the capillary bed
- blood pressure is higher at this end, whereas blood pressure is lower at the other end of the capillary bed closest to the venule (the smallest of veins)
- this pressure differential creates pressure filtration, where pressure at the arteriole end is high enough to opeb gaps btwn cells that make up the wall of the capilary. At the same time, the lower pressure at the venule side allows much of the tissue fluid to drain back into the capillary bed
- excess tissue fluid is drained into the LYMPH DUCTS
What are lymph ducts?
Excess tissue fluid does not reenter the capillary bed (preventing fluid build-up) but instead enter into small tubes called lympathic capillaries:
- thin walled, contain gaps btwn adjacent cells to facilitate easy movement of water, solutes
- fluid that enters the lympathic capillaries are called LYMPH
- there are internal one-way valves to keep fluid moving in one direction
- rely on skeletal muscle contractions and one way valves to keep the lymph moving
- lymph vessels join back into larger lymph ducts, eventually taking the fluid back to veins to become tissue fluid once again
- sometimes the lymph are passed through lymph nodes, filtering bacteria, viruses etc
Diff btwn single/double circulation + examples of each
Single - fish
Double - humans
Single:
- 2 chambered heart, 1 to receive and the other to pump blood
- Limitation: loss of blood pressure when blood is in capillaries of gills (for o2, co2 exchange)
Double:
- 4 chambered heart
- one side is in charge of pumping blood to/from the lungs for reoxygenation (PULMONARY CIRCULATION), the other side pumps blood to/from the body to supply oxygen/remove co2 (SYSTEMIC CIRCULATION)
- allows blood pressure to be restored
Practice identifying the structure of the heart + trace blood flow
Pearson pg 321
Parts: Cardiac muscle, pacemaker, LR Atria, LR/LRAV Ventricles, LR semilunar valves, septum, Coronary vessels, SI vena cava, aorta, pulmonary/LR artery, pulmonary veins
Blood flow:
Right side: SI vena cava > RA > RAV > RV > RSV > Pulmonary artery > LR pulmonary artery
Left side: Pulmonary veins > LA > LAV > LV > LSV > Aorta
Describe the adaptations/structures of the heart (8)
Cardiac muscle - thick, vascular muscle that is especially thick at the ventricles, most thick at the left ventricle to pump blood to the entire body
Coronary vessels - provide oxygenated blood to the heart muscle
Pacemaker (SA node) - Sinoartrial node (SA) located in the thin muscle wall of right atrium generates a spontaneous impulse to start each heartbeat
Atria - Thin muscular chambers designed to receive low pressure blood from the capillaries of the lungs (LA)/body (RA), sending blood to the ventricles
Ventricles - thick muscular chambers that pump blood out under pressure to lungs/body
Atrioventricular valves - one-way valves located btwn the atria and ventricles, close during each heart cycle to prevent backflow of blood to the atria
Semilunar valves - one-way valves located btwn ventricles and pulmonary artery(RSV)/aorta (LSV), closing after the surge of blood into the pulmonary artery/aorta to prevent backflow of blood into the ventricles
Septum - wall of muscular, fibrous tissue separates the left/right side
Describe the cardaic cycle controlled by SA (Essay)
Frequency of cardiac cycle = heart rate = bpm
Chamber of heart contracts > increase in BP > blood leaves chamber through any avliable opening (SYSTOLE) > cardiac muscle relaxes > BP decrease > blood rushes into chamber (DIASTOLE)
Both atria and both ventricle undergo Systole separately
SA node is independent of the nervous system, able to cause spontaneous contractions, but is unable to control the timing of the contractions.
- the action potentials from the SA node spread out almost instantly, resulting in atria undergoing systole > the action potential reaches atrioventricular node > AV node receives and delays the action potential by 0.1s, then sends out action potentials to both ventricles
AV node is located in in the right atrium, in the septum btwn left/right atria
As the ventricles have thicker muscle cells than atria, there is a system of conducting fibres the AV node traveling down the septum to the 2 ventricles. At various points the fibres have branches that spread out to the cardiac muscle tissue at the ventricles, causing the ventricles to undergo systole.
Describe how xylem root pressure works
Root pressure is a positive pressure potential, causing water movement in stems and roots when transportation in the xylem due to transpirational pull is not sufficient e.g. when high humidity prevents transpiration or when leaves are not present.
- Root cells create a low water potential by actively transporting mineral ions from cell to cell.
- this causes water to follow these movements by osmosis as there is a low water potential, creating a positive fluid potential to push water up the xylem
Describe adaptations of phloem sieve tube cells and companion cells for translocation of sap
Sieve plates:
- connected to companion cells by plasmodenta, allowing companion cells to give proteins and ATP
- greatly reduced cytoplasm, organelles and cell membrane
- no nucleus
Companion cells:
- increased amt of mitochondria
- the movement of sugars into the sieve tube elements create a low water potential, causing water to be pulled up, moving from an area of higher to lower water potential by osmosis.
- the water, rich in sugars, transports the sugars are needed for energy and storage
