B3 Flashcards
What are the three types of tissue?
Epithelial, muscle and nerve
What are the three main types of epithelial tissue?
Squamous epithelium
Columnar epithelium
Endothelium
What is the function of the epithelial tissue?
To line the outer surfaces of organs throughout the body, as well as the inner surfaces of cavities in many internal organs and blood vessels
Describe the structure and function and function of the squamous epithelium
- Made from specialised flattened squamous epithelial cells packed closely together.
- Forming a thin, flat and smooth layer that is one cell thick.
- Squamous epithelial tissue forms the thin walls of alveoli (small air sacs) in the lungs. This provides a large surface area for gas exchange.
- The one cell thick layer allows a rapid rate of diffusion of oxygen from the air (inside the alveoli) into the blood, and rapid diffusion of carbon dioxide from the blood into alveoli prior to breathing out.
- This tissue receives a good blood supply which helps to maintain a concentration gradient between alveoli and oxygen (and carbon dioxide) levels in the blood.
Label three squamous epithelial cells and then show the direction of diffusion of oxygen and the direction of diffusion of carbon dioxide. Indicate where O2 concentration is initially highest and where CO2 concentration is initially highest.
Explain how the structure of the squamous epithelial tissue supports its function in the lungs
What does COPD stand for?
Chronic obstructive pulmonary disorder
Which tissue is damaged if a patient has COPD?
Squamous epithelium
What are the symptoms of COPD and which illnesses are they associated with?
Breathlessness (emphysema)
Persistent coughing (emphysema and chronic bronchitis)
Excess phlegm/ mucus production (chronic bronchitis)
Chronic bronchitis and emphysema are both types of COPD
Which of the images show a healthy lung and which is from someone with emphysema? Explain your answer
A is the healthy lung sample as you can see many small alveoli.
B is a sample of lung from someone with emphysema as there are large spaces where the walls of the alveoli have broken down reducing the surface area.
What are the main features of emphysema?
Main cause is smoking
Damages the squamous epithelium lining of the alveoli
Leads to thickening/ scarring of alveoli walls
Inflammation of alveoli
Abnormally large air spaces in the lungs
Decreased surface area so less gas exchange
Alveoli loose elasticity so they cannot stretch and recoil
Difficulty breathing (breathlessness)
What are the features of chronic bronchitis?
- Inflammation of the airways in the lungs
- Squamous epithelium thickens
- Excessive secretion of mucus resulting in a cough
- Blocked airways leading to difficulty breathing
What is the cell labelled A?
Goblet cell
Describe the structure and function of ciliated columnar epithelium
Ciliated columnar epithelial tissue is made from column shaped epithelial cells
Tissue is one cell thick and lines trachea (windpipe) to protect lungs from infection.
These column shaped cells have many thin hair-like structures called cilia
The cilia produce rhythmic ‘rapid wave like motions’ to move mucus and trap pathogens (and unwanted particles), moving against air flow stopping them reaching the alveoli
What is the function of the goblet cells?
They make and secrete sticky mucus which helps to keep the lungs moist
Draw and label a ciliated epithelial cell
Explain how the structure of the columnar epithelial tissue supports its function in the lungs.
Where is squamous endothelial tissue located?
The inside layer of arteries and veins
Why is the endothelium lining smooth?
Reduces friction and allows smooth blood flow
Why do the chemicals that endothelial cells release do?
They allow the artery or vein wall to relax or contract (affects lumen diameter). This will regulate blood flow and blood pressure
Describe the structure and function of the capillaries.
Endothelium on it’s own forms the wall of the capillaries, which is one cell thick
The capillary wall has a short diffusion pathway for useful molecules such as glucose and amino acids to diffuse out of the blood into the body cells
What is the function of the squamous epithelium?
Thin, flat and smooth =
alveoli walls one cell thick =
short diffusion pathway for
O2 and CO2 to diffuse across
What is the function of the ciliated columnar epithelium?
Cilia are thin hair-like extensions from cell membranes that waft/ move material
What is the function of the endothelium?
Smooth inner lining of arteries + veins = reduces friction with blood. Easy exchange (capillaries)
Where in the human body is squamous epithelium found?
Alveoli (small air sacs in the lungs)
Where in the human body is the ciliated columnar epithelium found?
Trachea, bronchioles, bronchi (respiratory system)
Where in the human body is the endothelium found?
Arteries
Veins
Capillary wall
What is an example of when squamous epithelium tissue does not function correctly?
Emphysema = alveoli walls break down (big air spaces in lungs = smaller SA for gas exchange)
What is an example of when ciliated columnar epithelium does not function correctly?
Chronic bronchitis
What is an example of when endothelium does not function correctly?
Start of atherosclerosis
Thrombosis
Damage to what tissue triggers atherosclerosis?
endothelium
How does atheroma increase blood pressure?
Causes the artery wall the thicken and harden
Describe the development of atherosclerosis.
- Excess saturated fatty acids and low-density lipoproteins (LDLs, so called ‘bad cholesterol’) in the diet over a long period of time can cause plaques to build up in the wall of the artery (under the endothelial layer).
- This damages the endothelium and results in the formation of an atheroma.
- This triggers an inflammatory response and the migration of a type of white blood cell called macrophages to the site of damage.
- These macrophages become ‘foam cells’ that sink into the artery wall and then phagocytose the accumulated cholesterol inside the atheroma.
- The atheroma builds to such a size as to reduce the size of the lumen, so reducing blood flow and therefore increase blood pressure.
- Over time, the presence of atheroma causes the artery wall to thicken and harden.
- If the atheroma plaque ruptures then the plaque may pass to other blood vessels, blocking them and restricting their blood flow.
- This is called thrombosis and can lead to a stroke if the blood vessels are blocked in the brain, as neurones do not receive oxygen or glucose and so die.
- If the coronary arteries are blocked, this can lead to the death of cardiac muscle tissue (lack of oxygen and glucose), which may lead to a heart attack.
Define the term atheroma
Fat deposits/plaque that has built up in the wall of the artery under the endothelial layer, reducing the size of the lumen of the artery, reducing blood flow.
Define the term atherosclerosis
The pathological condition of the arteries that is characterized by the build up of (multiple) fat deposits and atheroma in the lining of blood vessels.
How does smoking increase the risk of atherosclerosis?
- The nicotine and carbon dioxide in cigarette smoke can directly damage the endothelium and trigger the same chain of events that leads to atherosclerosis and potentially rupture of the atheroma.
- In addition to the direct damage of the endothelium:
Carbon monoxide in cigarette smoke binds to haemoglobin so lowers the amount of oxygen the blood can carry, meaning the heart must also work harder.
Nicotine is a stimulant that mimics acetylcholine (discussed in later in this booklet) causing an increase in heart rate and blood pressure.
What is labelled A in the diagram?
Nucleus
What is labelled C in the diagram?
Mitochondria
What is labelled D in the diagram?
Sarcolemma
What is labelled E in the diagram?
Myofibril
Describe and explain the structure of a muscle fibre
- Skeletal muscle is composed of muscle fibres bound together by connective tissue.
- Each muscle fibre is surrounded by a cell membrane called a sarcolemma and its lots of nuclei are found just beneath
- A muscle fibre contains cytoplasm called sarcoplasm and within this is a collection of myofibrils which run parallel to each other along the length of the muscle fibre
- Surrounding each myofibril is sarcoplasmic reticulum which contains Ca2+ ions
- The sarcoplasm of the muscle fibre contains a large number of mitochondria (aerobic respiration to produce ATP) which supplies energy for muscle contraction
What is the name of the thick filament in a myofibril?
Myosin
What is the name of the thin filament in a myofibril?
Actin
What happens to the length of the sarcomere when the muscle contracts?
It shortens