LYMPHATIC SYSTEM

Question 1

INTERSTITIAL FLUID

Answer 1

Fluid found between the cells.

Question 2

CHYLE

Answer 2

The fat-laden creamy-looking lymph fluid leaving the gut through the small intestine.

Specialised lymphatic capillaries called lacteals are found in the folds of the small intestine
Lacteals absorb lipid (fat) products from digested food.

Question 3

RED BONE MARROW

Answer 3

• In adults, red bone marrow is found inside flat bones (e.g. ribs, pelvis) and the ends of long bones (e.g. humerus, femur)
• Haematopoietic stem cells give rise to all of our white blood cells (and red blood cells and platelets

Question 4

THYMUS GLAND

Answer 4

• Found in the mediastinum above the heart
• Surrounded by a connective tissue capsule with inward projecting trabeculae
• Function is to produce thymic hormones
• Thymic hormones thought to promote the maturation of T lymphocytes

When is the immune system at its most active?
➢When it is being established during childhood
➢ As a result, the functional part of the thymus is at its largest in childhood
➢ After childhood the functional portion of the thymus decreases in size, and fat takes its place
➢ This is known as ‘age involution’

Question 5

LYMPH NODE

Answer 5

Found along the lymph vessels
Large clusters occur in cervical, mammary, axillary and groin regions
Are bean-shaped structures that receive lymph from afferent (entering) lymph vessels
Lymph nodes filter lymph and activate the immune system
The lymph leaves the node via efferent vessels

There are ~600 lymph nodes scattered throughout the body!
Lymph flow through a node is one way

Surrounded by a connective tissue capsule
• Trabeculae project inward from the capsule to form compartments
• Each compartment or lobule is made up of a framework of reticular fibres synthesised by reticular cells
• The reticular fibre framework supports a population of macrophages and lymphocytes
– Macrophages can identify ‘non-self’ cells, engulf and destroy them
– Lymphocytes can identify pathogens, activate a specific immune response, and form ‘memory’ of that response for future infection

Question 6

TONSILS

Answer 6

Tonsils - surround the opening to the respiratory and
digestive tracts and filter incoming air
Five tonsils:
➢ 1 Pharyngeal or Adenoid
(on the posterior wall of the nasopharynx)
➢2 Palatine
(either side of the oral cavity) ➢2 Lingual
(at the base of the tongue)

Question 7

SPLEEN

Answer 7

Located on left side of abdominal cavity below the diaphragm
The Spleen Filters Blood
• Comprised of:
➢ Reticular cells – produce reticular framework
➢ Red pulp - removes worn out platelets and red blood cells, stores platelets, produces blood cells in the foetus
➢ White pulp – carries out immune function and removes blood borne pathogens

Question 8

LYMPH

Answer 8

Excess fluid via the lymphatic capillaries and lymph vessels which collect this excess fluid to form lymph

Question 9

OSMOTIC PRESSURE

Answer 9

Many blood proteins such as albumin are too large to leave the capillaries and create an osmotic pressure that pulls interstitial fluid back into the blood capillaries at the venous end

Question 10

LYMPH FLOW

Answer 10

The right lymphatic duct drains the upper right side of the body and right arm
• The right lymphatic duct returns fluid to the right subclavian vein (and heart)
• The left thoracic duct drains the rest of the body
• The left thoracic duct returns fluid to the left subclavian vein (and heart)

Question 11

LACTEALS

Answer 11

Specialised lymphatic capillaries called lacteals are found in the folds of the small intestine
• Lacteals absorb lipid (fat) products from digested food
• The fat-laden creamy-looking lymph fluid leaving the gut is called chyle

Question 12

MAST CELL

Answer 12

• the mast cell is the same as the basophil cell of blood
• when a tissue becomes injured mast cells release a number of chemicals important in inflammation
• basophil (BĀ-sō-fil) The least common type of white blood cell characterised by a pale nucleus and large granules that stain blue-purple with basic dyes.

Question 13

VASODILATION

Answer 13

Widening of the blood vessels.

Two immediate changes occur in the blood vessels in a region of tissue injury: vasodilation (increase in the diameter) of arterioles and increased permeability of capillaries. Increased permeability means that substances normally retained in blood are permitted to pass from the blood vessels. Vasodilation allows more blood to flow through the damaged area, and increased permeability permits defensive proteins such as antibodies and clotting factors to enter the injured area from the blood. The increased blood flow also helps remove microbial toxins and dead cells.

Question 14

HISTAMINE

Answer 14

Granules of mast cell and basophils. Released in the response to mechanical injury, presence of certain microorganisims, and chemicals released by neutrophils.

Promotes vasodilation of local arterioles. Increases permeability of local capillaries, promoting exudate formation.

Question 15

PHAGOCYTE

Answer 15

A type of white blood cell that engulfs bacteria and cell debris.

Engulf cells (may be fixed or wandering macrophages)

Question 16

CHEMOTAXIS

Answer 16

Chemotaxis. Phagocytosis begins with chemotaxis (kē-mō-TAK-sis), a chemically stimulated movement of phagocytes to a site of damage. Chemicals that attract phagocytes might come from invading microbes, white blood cells, damaged tissue cells, or activated complement proteins.

A chemical trail is left for white blood cells to follow – Chemotaxis

Question 17

EMIGRATION

Answer 17

White blood cells leave blood vessels to the area of tissue injury via a process called emigration

Within an hour after the inflammatory process starts, phagocytes appear on the scene. As large amounts of blood accumulate, neutrophils begin to stick to the inner surface of the endothelium (lining) of blood vessels (figure 22.10). Then the neutrophils begin to squeeze through the wall of the blood vessel to reach the damaged area. This process, called emigration (em′-i-GRĀ-shun), depends on chemotaxis

Question 18

HYPEREMIA

Answer 18

Excess of blood in the blood vessels in a specific part of the body.