Human Body Flashcards - Weeks 6 to 10

Semester 1 Year 1 Revision

What is blood and what is it made up of?

A transportation network that protects the body through clotting and inflammation. It regulates temperature and fluid balances and is the body’s fluid connective tissue. It’s made up of 55% plasma and 45% formed elements (created in red bone marrow)

What is plasma?

It is 92% water and solutes but also contains plasma proteins, nutrients, electrolytes, blood gases, hormones and nitrogenous wastes. It is a clear yellow fluid with an extracellular matrix

What is osmolarity?

The concentration of products that can’t pass out through blood vessel walls. It maintains blood volume, blood pressure and bodily fluids.

* Too high = blood absorbs too much water (high BP)
* Too low = blood loses water to tissues (oedema occurs and blood volume and blood pressure drop)

Describe erythrocytes.

They are anucleate (no nucleus) biconcave red blood cells with no mitochondria. It is flexible, allows stacking and a smooth flow.

* Each RBC has millions of haemoglobin molecules. Each haemoglobin molecule has 4 globin protein chains that bind to a haem group (iron). Each haem binds one O2 molecule, so 1 RBC has more than a billion O2 molecules on it

Describe erythropoiesis.

The process of making RBC’s. Haemopoietic stem cells synthesise haemoglobin, erythrocyte colony-forming units lose the nucleus and organelles and it’s released into blood as an immature RBC called a reticulocyte that eventually becomes a mature erythrocyte

Describe the structure of a vein.

Has venules where capillary beds join to form veins, thin-walled, large lumens with a thin tunica media (because BP is low) and a thick tunica externa. There are also valves to prevent backflow

What is the thoracic pump?

When the chest expands on inhalation, thoracic pressure drops below the abdominal cavity which compresses the abdominal inferior vena cava to move blood back upwards

What is the skeletal muscle pump?

Contracted muscles press on veins, forcing blood forward which opens valves which will close when blood starts to backflow

What are capillaries?

They link arteries to veins and allow fluid, electrolytes, nutrients, wastes and gases to be exchanged. The endothelium (tunica interna) rests on a basement membrane

What is the tunica interna?

Simple squamous cells that line the lumen of vessels. It’s smooth/shiny to reduce friction between blood and the vessel which avoids activating clotting which would occur if this surface was rough

What is the tunica media?

It controls vasodilation and vasoconstriction. Smooth muscle/elastic fibres expand and recoil to adjust to blood volume

What is the tunica externa?

The outermost layer that protects, reinforces and anchors the vessel to other structures, made of loose connective tissue

What is the heart?

The cardiovascular system’s pump that transports oxygen, nutrients and waste around the body. It’s in the thoracic cavity, in the mediastinum between the lungs and under the sternum

What is the pericardium?

A double walled sac around the heart. The pericardial cavity is the space between the parietal and visceral pericardium, and it lubricates membranes and allows the heart to beat with minimal friction

What are the 3 layers of the heart wall?

1. Endocardium - Lines the heart and its valves (simple squamous epithelium)
2. Myocardium - Middle layer composed of cardiomyocytes that narrow and shorten the heart when they contract.
3. Epicardium - Thin and transparent with areas of adipose tissue containing blood vessels

Describe the function of the left and right atrium.

They receive blood from veins (superior/inferior vena cavas and pulmonary veins). They are smaller and thin walled, and separated by the interarterial septum

Describe the function of the left and right ventricles.

They pump blood to the pulmonary arteries and the aorta to be distributed to the lungs or to the rest of the body and are separated by the interventricular septum

What are the sulci?

They are grooves filled with fat and coronary vessels. The coronary sulcus encircles the heart, separating the atria from the ventricles. The interventricular sulci is a boundary between the left and right ventricles

What is the pulmonary circuit?

Blood is pumped to the lungs through the pulmonary arteries and returns to the heart through the pulmonary veins

What is the systemic circuit?

Blood is pumped to the body through the aorta to release oxygen and nutrients and receive wastes. It returns through the superior and inferior vena cavas

What are the coronary arteries?

The first arteries coming off the aorta that follow the sulci, encircling the heart and supplying blood to heart tissue during ventricular relaxation

What are the heart valves?

Dense connective tissue covered by the endocardium that ensures one-way blood flow by opening and closing in response to heart contraction and relaxation. There are 4 heart valves, the tricuspid, pulmonary valve, mitral and aortic valves, all with 3 cusps except the mitral valve

What is ventricular contraction and relaxation?

Contraction - Blood is forced against the valve flaps, causing them to close to prevent backflow into the atrium

Relaxation - The aortic and pulmonary valves fill with the backflow of blood and close

How are heart sounds created?

Through the closing of heart valves. The “lubb” sound is the mitral and tricuspid valves closing and the “dubb” sound is the aortic and pulmonary valves closing

Describe the function of the sinoatrial node (SA).