Overview of the thorax

Question 1

Where is the thoracic vertebrae located?

Answer 1

• Compose the middle segment of the vertebral column (spine) - located between the cervical and lumbar vertebrae.
• In humans there are 12 thoracic vertebrae, are intermediate in size and increase in size going towards the lumbar vertebrae (lower ones a lot larger than upper).
• Numbered T1-T12 with T1 closest to the skull

Question 2

What is the sternum? (also known as the breast bone)

Answer 2

• Long flat bone, shaped like a males neck tie, located in the centre of the chest. The top of sternum supports the clavicle.
• Connects to the first seven pairs of ribs via cartilage and therefore helps to protect the heart, lungs and major blood vessels from injury.
• It consists of three regions: the manubrium, the body and the xiphoid process.

Question 3

What structures enter the thorax?

Answer 3

• The trachea enters the thorax to connect with the lungs, and the esophagus travels through it to connect with the stomach below the diaphragm.

Question 4

What are the heart and lungs also known as?

Answer 4

• Also known as circulatory and respiratory systems.

Question 5

How many pairs of ribs?

Answer 5

• 12 (therefore 24 rib bones).

Question 6

What is the thorax?

Answer 6

• The upper part of the trunk between the neck and the abdomen; it is separated from the abdomen by the diaphragm.
  It is formed by the 12 thoracic vertebrae, the 12 pairs of ribs, the sternum and the muscles and fasciae attached to these.
• The principal organs in the thoracic cavity are the heart with its major blood vessels and the lungs with the bronchi that bring in the body’s air supply.

Question 7

What are the different rib categories?

Answer 7

• True, false and floating.

Question 8

How are rib categories defined?

Answer 8

• By their size and how the connect to the front of the skeleton.

Question 9

Which are the true ribs and how do they connect?

Answer 9

• The first 7 pairs of rib bones (beginning at the top of the sternum) are known as true ribs. They connect to the spine by ligaments at the back and connect to the sternum by costal cartilage at the front.
• Costal cartilage is elastic and allows the rib cage to expand during respiration.

Question 10

Which are the false ribs and how do they connect?

Answer 10

• Ribs 8, 9 and 10 are false ribs. Like true ribs false ribs are connected to the spine at the back but differ as at the front they connect to the lowest true ribs instead of the sternum.
• False ribs are shorter than true ribs.

Question 11

What are the floating ribs and how do they connect?

Answer 11

• Ribs 11 and 12 are floating ribs and are the smallest of all rib bones. They are connected to the spine at the back but are not connected to anything at the front.

Question 12

What are the viscera?

Answer 12

• The soft internal organs of the body, especially those contained within the abdominal and thoracic cavities e.g. intestines.

Question 13

What is fasciae?

Answer 13

• Band or sheet of connective tissue fibres, primarily collagen. forms beneath the skin to attach, stabilise, enclose and separate muscles and other internal organs (surrounds them).
• Made up of fibrous connective tissue containing closely packed bundles of collagen fibres oriented in a wavy pattern parallel to the direction of pull. These are strong and flexible.

Question 14

What are ligaments?

Answer 14

• Collagen is major component. Fibrous connective tissue that joins one bone to another bone (or cartilages). Holds joint together.

Question 15

What are tendons?

Answer 15

• Fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Collagen main component. Flexible but inelastic.

Question 16

Name the muscles of the thoracic wall.

Answer 16

• There are five muscles that make up thoracic cage. Intercostals (these muscles arranged as three layers BETWEEN ribs - external, internal and innermost), transversus thoracis and subcostals.
• external intercostals = 11 pairs, run from rib above to rib below. Elevate ribs increasing thoracic volume. Supplied by intercostal nerves T1-T11.
• internal intercostals = closer to sternum than external intercostals. Flat. Run from rib above to rib below. Run in different direct to externals. Interosseous part reduces thoracic volume by depressing rib cage while interchondral part elevates ribs. Supplied by same nerves as externals.
• innermost = deepest of the three. Structure similar to internals. Separated from internals by intercostal neurovascular bundle. Run from rib above to rib below. Supplied by same nerves.
• transversus thoracis = attached from the posterior surface of the inferior sternum in the internal surface of costal cartilages 2-6. They weakly depress the ribs. Supplied by same nerves as above.
• subcostals = found in inferior portion of thoracic wall. They comprise of thin slips of muscle, run from internal surface of one rib to second and third ribs below. Share the action of internal intercostal muscles. Supplied same nerves.
• Don’t forget the diaphragm. The diaphragm closes the thoracic outlet and separates the thoracic cavity from the abdominal cavity.

Question 17

What are the three layers of intercostal muscles?

Answer 17

• Internal, external and innermost.

Question 18

What is the function of the intercostal muscles?

Answer 18

• They are important in respiration and important in keeping the intercostal space rigid.

Question 19

What is the diaphragm?

Answer 19

• Sheet of internal skeletal muscle, dome shaped, that extends across the bottom of the thoracic cavity.
• Separates the thoracic cavity and the abdominal cavity.
• Important function in respiration as chief muscle in inspiration: as diaphragm contacts the volume of thoracic cavity increases and air is drawn to the lungs.
• Attaches to sternum, bottom 6 ribs and the vertebral column.

Question 20

During inspiration what happens?

Answer 20

• Diaphragm moves down, increasing the intrathoracic volume.
• Intercostal muscles contract increasing intrathoracic volume.
• These movements result in decreased intrathoracic pressure and so air is pulled into the lungs.

Question 21

What is the pleura?

Answer 21

• A serous membrane divided into parietal (outer) and visceral (inner) layers (the visceral layer sits directly on top of lung) which surround the lungs and contain the pleural cavities.
• These two layers are also separated by small amounts of serous fluid.
• Serous fluid function: reduces pain and friction.

Question 22

What is pleuritis (pleurisy)?

Answer 22

• Inflammation of the pleura. The lung surfaces end up so rough the ‘pleural rub’ can be heard with a stethoscope. Leads to chest pain (usually sharp) when you take a breath or cough.

Question 23

Which lung is smallest and why?

Answer 23

• Left: due to being on same side as the heart.

Question 24

How many lobes does each lung have?

Answer 24

• Right lung has three lobes and left lung has two lobes.

Question 25

What are the right lung lobes called?

Answer 25

• Superior, middle and inferior.

Question 26

What are the left lung lobes called?

Answer 26

• Superior and inferior.

Question 27

How are right lung lobes separated?

Answer 27

• The superior and middle lobes are separated by the horizontal fissures whilst the middle and inferior lobes are separated by the oblique fissures.

Question 28

How are left lung lobes separated?

Answer 28

• The superior and inferior lobes are separated by the oblique fissures.

Question 29

What is interesting about each lung lobe?

Answer 29

• Each has its own blood and air supply.

Question 30

What is a lung and where is it situated?

Answer 30

• Primary organ of respiration. Each have two lungs. Situated in thoracic cavity of chest. Rest on the diaphragm. Cardiac notch may be found on anterior surface of left lung due to rubbing with heart.

Question 31

What is the trachea and what is its function?

Answer 31

• Supplies air to the lungs through mouth. 20 c-shaped rings of cartilage in its wall, reinforce front and sides to protect and maintain airway and leaves membranous wall at back. (This is so food can move down back without being restricted by trachea cartilage). Divides into right and left main (primary) bronchi. The gaps between the rings are filled by trachealis muscle (bundle of smooth muscle and fibroelastic tissue) allowing flexibility during inspiration and expiration.

Question 32

What is the bronchus?

Answer 32

• Is a passage of airway in the respiratory tract that conducts air into the lungs.
• The primary of main bronchus branches into two. The right bronchus is more vertical and wider than the left bronchus (these branches go into the lungs).
• The Bronchus then divides into secondary bronchi supplying each lobe of the lung (three secondary bronchi on the right and two secondary bronchi on the left).
• These bronchi then further divide into smaller and smaller tubes called bronchioles. The bronchioles end in microscopic airsacs (alveoli). These air sacs are lined with mucus and are surrounded by a network of blood capillaries. Gas exchange occurs at alveoli.

Question 33

What is the role of blood?

Answer 33

• To provide the body with oxygen and nutrients and also to assist in the removal of metabolic wastes.

Question 34

Describe the structure of the heart?

Answer 34

• Divided into 4 chambers: upper left and right atria and lower left and right ventricles.
• Blood flows one way through heart due to presence of heart valves which prevent back flow.
• Heart is enclosed in protective sac called pericardium.
• Heart wall is made up of three layers: epicardium, myocardium and endocardium.

Question 35

How do you calculate cardiac output (the amount of blood pumped)?

Answer 35

• Heart rate x stroke volume.

Question 36

What is the septum?

Answer 36

• Separates the two sides of the heart. The portion that separates the two upper chambers (right and left atria) is called the atrial (or interatrial) septum. The portion that separates the two lower chambers (right and left ventricles) of heart is called the ventricular (or interventricular) septum.

Question 37

What do the atria do?

Answer 37

• “Collect the blood”

- Atria receive blood from either the vena cava or the pulmonary vein.

Question 38

What do the ventricles do?

Answer 38

• Pumps blood out of the heart through the aorta or the pulmonary artery.

Question 39

Which side of the heart receives well-oxygenated blood and which receives poorly-oxygenated blood?

Answer 39

• The right side of the heart receives poorly (or de-) oxygenated blood and pumps it to the lungs while the left side receives well oxygenated blood from the lungs and pumps it to the rest of the body.

Question 40

What are the three types of blood vessel?

Answer 40

• Arteries (carry blood away from heart), capillaries (enable actual exchange of water and chemicals between blood and tissues) and veins (which carry blood from capillaries back towards the heart).

Question 41

What do arteries do?

Answer 41

• Carry blood away from the heart (always oxygenated apart from the pulmonary artery which goes to the lungs), thick muscular walls, small passageways for blood (internal lumen), contain blood under high pressure.

Question 42

What do capillaries do?

Answer 42

• Found in the muscles and lungs, microscopic: one cell thick, very low blood pressure, where gas exchange takes place (oxygen passes through the capillary wall and into the tissues, carbon dioxide passes from the tissues into the blood).

Question 43

What do veins do?

Answer 43

• Carry blood to the heart (always de-oxygenated apart from the pulmonary vein which goes from the lungs to the heart), have thin walls, have larger internal lumen, contain blood under low pressure and have valves to prevent blood flowing backwards.

Question 44

What are the 4 key components of blood?

Answer 44

• Plasma, red blood cells, white blood cells and platelets.

Question 45

What is plasma?

Answer 45

• Fluid part of blood.

- Carries carbon dioxide, hormones and waste.

Question 46

What are red blood cells?

Answer 46

• These contain haemoglobin which carries oxygen. Made in the bone marrow. The more you train the more red blood cells are made.

Question 47

What are white blood cells?

Answer 47

• Most made in the bone marrow. Important part of the immune system, they produce antibodies and destroy harmful microorganisms. Two types of white blood cells, t and B cells (lymphocytes) are also produced in lymph nodes and spleen and T cells are produced and mature in the thymus gland.

Question 48

What are platelets?

Answer 48

• Clump together to form clots.

- Protect the body by stopping bleeding.

Question 49

What does blood do during exercise?

Answer 49

• Transports nutrients and waste.
• Delivers oxygen to the working muscles.
• Removes heat (temperature regulation).
• Dilutes/carries away lactic acid (acidic balance).

Question 50

What is the pericardium?

Answer 50

• Double walled sac containing the heart.
• The sac is divided into 2 layers: fibrous (outer) and serous (inner) pericardium.
• The space between the two layers is know as the pericardial cavity and contains serous fluid which protects the heart from any kind of external jerk or shock.
• The fibrous pericardium is tough and not dispensible. The serous pericardium lines the fibrous pericardium.

Question 51

What are the roles of the pericardium?

Answer 51

• Fixes the heart to the central compartment of the thoracic cavity, gives protection against infection and provides lubrication for the heart.

Question 52

What are the layers of the pericardium?

Answer 52

• Fibrous pericardium (outer): tough and cannot tear.

- serous pericardium (inner): lines the fibrous pericardium.

Question 53

What does the upper respiratory tract contain?

Answer 53

• The nasal cavity (large air filled space above and behind the nose).
• the pharynx (makes up part of the throat behind the nasal cavity. It is behind mouth and above esophagus and larynx).
• the larynx (voice box - involved in breathing, sound production and protecting trachea against food aspiration).

Question 54

What does the lower respiratory tract contain?

Answer 54

• trachea (windpipe - tube that connects the pharynx and larynx to lungs allowing passage of air).
• primary bronchi (these extend from the trachea, there is a right and left and lead into the lungs).
• lungs (spongy air filled organs located in wither side of the chest).

Question 55

What are the epicardium, myocardium and endocardium?

Answer 55

• Together they make up the tissue if the heart wall.
• epicardium = covering outer surface of heart also known as visceral pericardium which is the inner layer of the pericardium. It is a serious membrane that consists an external layer of simple squamous and an inner layer of areolar tissue. The squamous cells secrete lubricating fluids into pericardial cavity.
• myocardium = thick middle layer of heart wall. Consists of numerous layers of cardiac muscle fibres. Contraction of myocardium pumps blood out of heart into the aorta and pulmonary trunk arteries.
• endocardium = covers the inner surface of heart wall. Also covers heart valves and tendons and is continuous with the endothelium that lines the major blood vessels that attach to the heart.

Question 56

What is a serous membrane?

Answer 56

• Forms a smooth, transparent, two layered membrane lubricated by fluid derived from serum. E.g. Of serous membranes are peritoneum, pericardium and pleura.

Question 57

What does anterior mean?

Answer 57

• Near the front.

Question 58

What does posterior mean?

Answer 58

• Near the back.

Question 59

What does lateral mean?

Answer 59

• At the side.