Anatomy Pre-Reading Material Flashcards
Extra detail
What is the defining feature of the human circulatory system?
Closed double system
How is the circulatory system a closed system?
Blood is contained within the blood vessels (like in all vertebrae)
Substances enter and exit, but the blood tissue doesn’t
How is the circulatory system a double system?
Blood passes through the heart twice in a complete circulation
Blood travels through the pulmonary division to become oxygenated, returns to the heart, then travels through the systemic division to deliver oxygen to the bodily tissues
What are the names of the broad groups of blood vessels involved with the circulatory system?
Arteries, veins, and capillaries
What is the route (via blood vessels) that the blood takes form the heart?
Heart–>Arteries–>Arterioles–>Capillary bed–>Venules–>Veins–>Heart
What is the main role of the arteries?
To carry blood away from the heart
How are arteries well adapted for their job?
Thick walls to withstand the pressure generated by ventricular contraction
Narrow lumen to maintain high blood pressure needed to facilitate blood flow
Elastic muscle fibres in the walls, allowing the arteries to stretch and recoil in response to changing pressure
Smooth muscle to allow the arteries to constrict or dilate to adjust blood flow to an area
What is the name of the smallest arteries?
Arterioles
What is the physiological significance of the capillaries?
Site of exchange between the blood and the surrounding environment
What does the term “capillary bed” refer to?
The meshwork pattern of interconnecting capillaries throughout a tissue
What are some key features of capillaries?
Large surface area to volume ratio
As narrow as possible- only one erythrocyte wide
Very narrow wall (simple squamous epithelium)
Facilitate rapid transport
Bruises are aa result of damage done to capillaries
What is the relation between capillaries and arteries?
Blood travels from arteries to arterioles, and then capillary beds
Arteries can constrict or dilate to reduce or increase the amount of blood travelling into a capillary bed
What are capillary beds typically followed by and what is an exception?
Typically followed by venules (smallest veins)
The glomerulus in the kidney is a key exception, reflecting it different pressure and function (ultrafiltration)
Why are veins important for bloodflow?
Drain blood away from tissues, typically towards the heart but sometimes to a second structure before doing so
What are key features of veins?
Only need a thin wall as blood pressure inside them is so low
Wide lumen to accommodate a large volume of blood (approx. 70% of blood is in the veins)
Why do the veins accumulate a large volume of blood?
Partly due to slow flow of blood, but also acts as a reservoir which can be accessed when demand increases
What is the function of portal veins?
Drain blood from one capillary bed to deliver it to a second set of capillaries elsewhere
What is an example of a portal vein
Largest example is the hepatic portal vein
Drains blood from the intestines to the liver for detoxification of digested substances
What is the path of movement for fluids?
Move from areas of high pressure to areas of lower pressure
Fundamental mechanism controlling blood flow throughout the body
How does ventricular systole (contraction) affect blood flow?
Ventricular systole generates a large amount of pressure, so the blood flows from ventricles into the slightly lower pressure arteries
Why are semilunar valves important during ventricular diastole (relaxing)?
During ventricular diastole the ventricles are under low pressure, so the blood would flow back to them, and the semilunar valves prevent this from occurring
Why does the heart not pump blood through the veins?
pressure decreases further away form the heart, so the blood flows away from it through the arteries
Once it has passed through the capillaries most of the pressure generated by the heart has been lost
What are some of the various ways in which blood flows through the veins?
Skeletal muscle pumps: contractions cause the veins between them to squeeze blood out
Respiratory pump: changing pressure of the thorax during breathing. When breathing in the pressure in the thorax decreases drawing air into the lungs, and so draws blood into the thoracic veins from lower veins
Some veins travel along arteries. Arteries expand/recoil with the changing pressure through the cardiac cycle, and so press on the veins and squeeze the blood out of them
General movement of the body will cause blood in the veins in that area to move through momentum
Gravity can bring blood back to the heart, e.g., blood in the head and the neck will typically drop straight down into the superior vena cava
What is significant regarding the various ways that blood moves through the veins?
They do not necessarily make the blood move towards the heart and could instead cause blood to move backwards. Backwards flow of blood is prevented by one-way valves in the veins. If the blood must move and can’t go backwards, it will go forwards.
What are the three layers of tissue that make up the heart and where can they be found, and what are their features?
Endocardium (internal lining): an epithelium reducing resistance to blood flow on the inside of the heart
Myocardium (middle and largest portion): consists of cardiac muscle cells which contract to make the heart beat
Epicardium (outermost layer): also known as the visceral serous pericardium
What are the chambers of the heart called?
Right Atrium
Right Ventricle
Left Ventricle
Left Atrium
What is significant about the right and left side of the heart?
They are functionally and anatomically separate; blood does not flow directly from one side to the other
How are the four internal chambers separated?
Left and right atria are separated by the interatrial septum
Left and right ventricles are separated by the interventricular septum
How are the ventricles and atria connected to each other?
Atrioventricular valves (AV valves)
What is the pathway of blood drainage?
Blood drains from the veins into the atria
Right atrium receives deoxygenated blood from the inferior and superior vena cava
Left atrium receives oxygenated blood from the four pulmonary veins
When does the blood not drain into the ventricles from the atria?
During ventricular systole
What is the function of the ventricles in regards to blood flow?
Right ventricle pumps deoxygenated blood into the pulmonary trunk to travel to the lungs and become oxygenated
Left ventricle pumps oxygenated blood into the aorta to be distributed throughout the body
What is the relationship between blood flow and the atria?
Even when the atria are not contracting, blood will flow from them
Atrial systole moves the last of any pooled blood through, meaning that the AV valves are open throughout ventricular diastole, even when the atria are also relaxed
What are the great vessels?
Main arteries and veins connected to the heart
What is the respiratory system comprised of?
Lungs and airways
What can the respiratory system be divided into?
Upper respiratory system and lower respiratory system
How does air enter the respiratory system during inhalation?
Air enters the respiratory system via the nares (nostrils)
Enters the nasal cavities (separated from each other via the nasal septum), then enters the pharynx
What is an alternate route for air to enter the respiratory system?
Through the oral cavity
What is the pharynx and what can it be divided into?
The pharynx is the top of the throat and can be divided into the nasopharynx, oropharynx, and laryngopharynx (hypopharynx)
Where is each division of the pharynx found?
Nasopharynx, behind the nasal cavity
Oropharynx, behind the oral cavity
Laryngopharynx (hypopharynx), behind the larynx
What occurs when air moves into the larynx?
The larynx closes to prevent inhalation of solids and liquids
What is the larynx?
A complex cartilaginous structure
What is significant about the largest cartilage?
The thyroid cartilage, and can be felt as the “Adam’s apple” (laryngeal prominence)
What is the larynx also the site of?
The vocal cords, so is also often called the voice box
What is the significance of the vocal cords and what is the impact of this on the larynx?
The vocal cords are the boundary between the upper and lower respiratory system
For convenience, the larynx is often entirely grouped with the upper or lower respiratory system
Strictly speaking it is partly in both
Where does air move to after the larynx?
To the trachea
Where is the trachea and how can it be described?
Trachea runs down the centre of the thorax
C-shaped cartilages run down its length, with the ends joined by muscle tissue
What is significant about the muscle tissue and cartilages regarding the trachea?
Allows the trachea to have some flexibility whilst still being able to hold itself open
Where does the trachea end?
Terminates by dividing into the two primary bronchi (left and right)
Where do the primary bronchi go?
Each primary bronchus goes to a lung
What are features of the primary bronchi?
Similarly structured to the trachea
At the lungs each bronchus divides again into secondary/lobar bronchi, which supply each lobe of the lung
Further divide into tertiary/segmental bronchi, then continue to divide further into smaller branches
What occurs to the cartilage when the bronchi become smaller?
The proportion of cartilage in the bronchi decreases as they get smaller, eventually having none at the bronchioles
What is the function of the bronchioles?
Supply air to the alveoli, which is the site of gas exchange
How many alveoli are in the lungs?
Roughly 500,000,000
Why are alveoli beneficial for the lungs?
Provides the lungs with a large surface area, facilitating a high rate of gas exchange between the blood and the atmosphere
What occurs during exhalation?
Air moves back through these structures and exits via the nares/mouth
Why does breathing work?
Due to Boyle’s law which dictates that pressure and volume are inversely proportional to each other
How can Boyle’s law be expressed in simple terms?
Increasing the volume of a gas by stretching its container will decrease the pressure that acts upon it
Similarly decreasing the volume of the gas will increase the pressure on it
How is Boyle’s law demonstrated in the body?
The lungs can increase in volume to decrease pressure, and then they can decrease in volume to increase in pressure
What is a simplification of how Boyle’s law is related to the body and breathing?
“Pressure” is a technical term but simply means pressing/pushing/etc. When we press on something, we apply pressure to it. “Decreasing the volume of the lungs increases pressure in them, causing air to exit to the lower pressure
atmosphere” is just a more technical way of saying “Squashing the lungs by pressing on them pushes the air out”.
In which direction does air flow?
From an area of higher pressure to an area of low pressure
How do the lungs accommodate the gradient needed for air to enter?
Decreasing the pressure in the lungs below atmospheric pressure allows the air to enter from the higher atmospheric pressure, to the lower pressure of the lungs
What would occur if the pressure of the lungs was increased above atmospheric pressure?
The air would move out of the lungs and back to the external environment
How can the volume of the lungs increase during inhalation?
The lungs can increase in volume as they are attached to the rib cage and the diaphragm
Contraction of the external intercostal muscles causes the ribs to move upwards and outwards, thus increasing the volume of the thorax and so the lungs
Contraction of the diaphragm at the base of the lungs stretches the lungs downwards, directly increasing their volume
What type of process is exhalation?
Can either be a passive or forced process
What happens during passive inhalation?
External intercostal muscles and the diaphragm relax
This allows for the lungs to recoil due to their own elasticity, as well as the weight of the ribcage pressing back down on them
What is an example of forced inhalation, and what happens during forced inhalation?
A person is breathing out deliberately
They can breathe out more quickly by using the internal intercostal muscles to pull the ribs back inwards more quickly
