Mass transport Flashcards
How are single celled organisms adapted for gas exchange?
Single celled organisms have a high surface area to volume ratio for the exchange of substances to occur via simple diffusion
What are adaptations of gas exchange surfaces?
- a large surface area
- short diffusion pathway/ distance
- maintanice of a concentration gradient
What is a spiracle?
It’s an opening in the exoskeleton of an insect that has valves
It allows air to enter the insect and flow into the system of trachea - most of the time, the spiracles are closed to reduce water loss
What are trachea?
They are tubes within the insects’ breathing system, which leads to the teacheoles
How does gas exchange happen in insects?
A large number of tracheoles run between cells and into muscle fibres - the site of gas exchange
How is a diffusion gradient maintained?
A concentration gradient is created as oxygen is used by respiring tissue, allowing more to move in by the spiracles by diffusion
What happens for very active insects that need a more rapid supply of oxygen?
They create mass flow of air into the tracheal system:
- closing the spiracles
- using muscles to create a pumping movement for ventilation
What is the function that lactate plays during flight?
Lactate lowers water potential in the respiring muscle, which causes water to move into the muscles via osmosis, which allows gases to diffuse across more quickly
What is the structure of fish gills?
Series of gills on each side of the head, each gill arch is attached to two stacks of filaments. On the surface of each filament, there are rows of lamelle. The lmaelle surface consists of a single layer of flattened cells that cover a vast network of capillaries
What are the mechanisms of fish gills?
The capillary system within the lamelle ensures that the blood flow is in the opposite direction to the flow of water. It’s a counter-current system. The counter-current system ensures the concentration gradient is maintained along the whole length of the capillary. Twh water with the lowest oxygen concentration is found adjacent to the most deoxygenated blood
What is the structure of a leaf?
Waxy (waterproof) cuticle
Upper epidermis - layer of tightly packed cells
Palisade myseophyll layer - layer of elongated cells containing chloroplasts
Spongy mysophyll layer - layer of cells that contain an extensive network of air spaces
Stomata - press on the underside of the leaf, which allows air to enter
Guard cells - pairs of cells that control the opening and closing of the stomata
Lower epidermis - layer of tightly packed cells
What are the mechanisms for leaves of a dictyledonous plant?
- when guard cells are turgid, the stoma remains open, allowing air to enter the leaf
- the air spaces within the spongy mysophyll layer allow carbon dioxide to diffuse rapidly across into cells
- the carbon dioxide is quickly used up in photosynthesis by cells containing chloroplast - maintaining the concentration gradient
- no active ventilation required as the thiness of the plant tissues and the pressure of stomata helps to create a short diffusion pathway
Description of the trachea:
That airway that leads from the mouth to the nose to the bronchi. The trachea is lined with mucas - secreating goblet cells and cilla. The cilla sweep microorganisms and dust away from the lungs
Description of the lungs:
Humans have two lungs, both of which are a central part of the respiratory system and where gas exchange takes place
Description of the bronchi:
Bronchi is plural of bronchus. The left and right bronchi are at the bottom of the trachea and are similar in structure but narrower. The bronchi lead to bronchioles
Description of the bronchioles:
These are narrow tubes that carry air from the bronchi to the alveoli. As they are so narrow, they have no supporting cartilage and so can collapse
Description of the alveoli:
The main site of gas exchange in the lungs. These are tiny sacs with many structural adaptations to enable efficient gas exchange, such as their thin walls and large surface area to volume ratio
Description of the capillary network:
An extensive network of capillaries surrounds the alveoli and is an exchange surface between the lungs and the blood. During gas exchange, oxygen diffuses from the alveoli and into the capillaries, while carbon dioxide diffuses the other way and exhaled
Gas exchange tissues:
Cartilage is a strong and flexible tissue found along the tracheal rings
Ciliated epithelium found along the trachea down to the bronchi small projections of cilla, which sweep the mucas, dust, and bacteria upwards away from the lungs and epithelium
Goblet cells can be found scattered throughout the ciliated epithelium in the trachea
The alveoli have a lining of thin and sauamous epithelium that allows for gas exchange
Smooth muscle can be found throughout the walls of the bronchi and bronchioles, which helps regulate the flow of air
Each alveolus is surrounded by an extensive network of capillaries
Features of the alveoli:
-large number of alveoli which increases surface-area and diffusion area
-thin walls which results in a short diffusion pathway for gas exchange = quick and efficient
-extensive capillary network which are one cell thick keeping the diffusion pathways short, constant flow of blood maintains concentration gradient
passage of air:
nose/mouth –> trachea –> bronchi –> alveoli
Breathing in:
-causes volume in chest increases and the air pressure in the lungs to decrease
-as a result air moves down the pressure gradient and rushes into the lungs
mechanisms for at rest: the diaphragm contracts and flattens increasing chest volume
mechanisms when exercising: in addition to the flattening of the diaphragm the external intercostal muscles contract causing the rib cage to move upwards and outwards
Breathing out:
-when at rest breathing out occurs mostly due to the recoil of the lungs after they’ve been stretched
-volume in the chest decreases and pressure increases causing air to be forced out
mechanisms at rest: external intercostal muscles relax, the recoil of elastic fibres surrounding the alveoli causes air to be forces out, diaphragm becomes dome-shaped
mechanisms when exercising: internal intercostal muscle contract to pull the ribs down and back, abdominal muscle contract to push organs upwards against diaphragm increasing the internal pressure, this causes forced exhalation
Heart:
a hollow muscular organ located in the chest cavity that pumps blood. Cardiac muscle tissue is specialised for repeated involuntary contraction with rest
