Lymphatic System & Lymphatic System & ImmunityImmunity

LymphLymph is a specialized fluid formed in is a specialized fluid formed in tissue spaces. This fluid carries protein tissue spaces. This fluid carries protein molecules, immune cells, fat and molecules, immune cells, fat and excess tissue fluid called excess tissue fluid called interstitial interstitial fluid (IF)fluid (IF) back to the veins through back to the veins through lymphatic vessels.lymphatic vessels. IF is formed from IF is formed from blood plasma coming out of the blood plasma coming out of the capillaries under pumping pressure of capillaries under pumping pressure of the heart.the heart.

Lymphatic drainage prevents Lymphatic drainage prevents accumulation of too much tissue fluidaccumulation of too much tissue fluid

Lymphatic capillary is 1 cell layer thick.Lymphatic capillary is 1 cell layer thick.

Lymphatic vessels have 1 way flow (like Lymphatic vessels have 1 way flow (like veins).veins).

Right lymphatic ductRight lymphatic duct::- drains right upper quadrant into - drains right upper quadrant into

right right subclavian vein.subclavian vein.Thoracic duct:Thoracic duct:

- drains rest of body- drains rest of body- largest in body- largest in body- in abdomen Cisterna chyli - in abdomen Cisterna chyli

stores stores lymphlymph

Lymph is under low pressure as is Lymph is under low pressure as is the venous system.the venous system.

- contracting of skeletal muscle in - contracting of skeletal muscle in appendagesappendages

- contracting skeletal muscles used - contracting skeletal muscles used in breathing (intercostals) and in breathing (intercostals) and contraction of smooth muscle of contraction of smooth muscle of diaphragm.diaphragm.

- contraction of smooth muscle in - contraction of smooth muscle in larger lymphatic trunkslarger lymphatic trunks

Lymphatic tissue:Lymphatic tissue:

- lymph nodes- lymph nodes

- tonsils- tonsils

- spleen- spleen

- thymus- thymus

- bone marrow- bone marrow

Lymph nodes- oval or bean shaped.

- lymph that is drained from the body passes and is filtered through structures called lymph nodes.

- connective tissue called reticular fibers and are populated by dense aggregates of lymphocytes and macrophages.

-Lymph nodes occur along the entire length of the lymphatic system and tend to increase in size as they become closer to the thoracic duct. -arranged in chains or clusters

- scattered in groups; superficial and deep- scattered in groups; superficial and deep

- cervical- cervical

- submandibular- submandibular

- axillary- axillary

- inguinal (groin)- inguinal (groin)

- supratrochlear- supratrochlear

- filter lymph- filter lymph

- lymph flows into node from - lymph flows into node from afferent afferent lymphatic vessel.lymphatic vessel.

- exits from - exits from efferent lymphatic efferent lymphatic vesselvessel

Nodes contain large number of Nodes contain large number of macrophages and lymphocytesmacrophages and lymphocytes

Node has a medulla and a cortex.Node has a medulla and a cortex.

Germinal centers are responsible for Germinal centers are responsible for the proliferation of B-cells (remember the proliferation of B-cells (remember what they produce?)what they produce?)

- Distal portion of the small intestine:Distal portion of the small intestine:

- Peyer’s patches- Peyer’s patches

ThymusThymus

- bilobed structure located substernally - bilobed structure located substernally in mediastinumin mediastinum

- Immature T-cell lymphocytes (stem - Immature T-cell lymphocytes (stem cells)cells)

migrate from bone marrow to migrate from bone marrow to thymus thymus and mature under the direction and mature under the direction of of thymosin. Reside in lymph nodes.thymosin. Reside in lymph nodes.

- Transforms from large in size - Transforms from large in size (childhood) (childhood) and atrophies to fat and and atrophies to fat and connective connective tissue in adults- Involution. tissue in adults- Involution. Still Still produces mature T-cellsproduces mature T-cells

Spleen:Spleen:- largest lymphoid organ- largest lymphoid organ- upper left quadrant between stomach - upper left quadrant between stomach and diaphragmand diaphragm-Functions:-Functions:

- phagocytosis of bacteria- phagocytosis of bacteria- replace worn out RBC’s (120 days)- replace worn out RBC’s (120 days)- blood reservoir- blood reservoir- erythrocyte production in the fetus- erythrocyte production in the fetus- Stores blood platelets- Stores blood platelets

- Splenomegaly: enlarged spleen (EBV)- Splenomegaly: enlarged spleen (EBV)- Trauma from rib fx.= splenectomy - Trauma from rib fx.= splenectomy (removal of spleen)(removal of spleen)

Spleen is composed of two tissue Spleen is composed of two tissue types:types:

White pulp: composed of splenic White pulp: composed of splenic nodules that contain many nodules that contain many lymphocytes.lymphocytes.

Red pulp: rbc’s, lymphocytes and Red pulp: rbc’s, lymphocytes and macrophages. Give the spleen its macrophages. Give the spleen its reddish/purplish color.reddish/purplish color.

SpleenSpleen

Tonsils:Tonsils:

-Pharyngeal tonsil (adenoid) -Pharyngeal tonsil (adenoid) embedded in embedded in posterior wall of posterior wall of nasopharynx.nasopharynx.

- Palatine tonsil: tonsillectomy- Palatine tonsil: tonsillectomy

- Lingual tonsil: base of tongue- Lingual tonsil: base of tongue

Tonsils are first line of defense against Tonsils are first line of defense against bacteria entering the mouth - bacteria entering the mouth - tonsillitistonsillitis

Immunity:Immunity:Defending the body against invasion of Defending the body against invasion of

pathogenic substances and eliciting an pathogenic substances and eliciting an immune response when the body immune response when the body encounters those substances. encounters those substances.

1- Non specific immunity (primary defense)1- Non specific immunity (primary defense)- skin- skin- mucous membranes- mucous membranes- tears- tears- saliva- saliva- micturition (urinating)- micturition (urinating)- lysozyme in saliva and tears- lysozyme in saliva and tears- HCl in gastric juice in stomach - HCl in gastric juice in stomach - Vaginal pH.- Vaginal pH.

Specific Immunity: Immunity against Specific Immunity: Immunity against specific organismsspecific organisms

Specific immunity is more effective Specific immunity is more effective than the nonspecific methods, and than the nonspecific methods, and has a memory component that has a memory component that improves response time when an improves response time when an invader of the same type (or species) invader of the same type (or species) is again encountered.is again encountered.

Inflammatory responseInflammatory response Damaged cells release chemical signals Damaged cells release chemical signals

such as histamine that increase capillary such as histamine that increase capillary blood flow (vasodilation) into the affected blood flow (vasodilation) into the affected area (erythema and heat). The heat makes area (erythema and heat). The heat makes the environment difficult for microbes to the environment difficult for microbes to function, increases mobility of white blood function, increases mobility of white blood cells. Chemotaxis.cells. Chemotaxis.

Capillaries pass fluid into tissue spaces Capillaries pass fluid into tissue spaces (interstitial) causing the infected/injured (interstitial) causing the infected/injured area to swell (edema). Finally, area to swell (edema). Finally, macrophages (monocytes outside the macrophages (monocytes outside the blood) clean up dead microbes, cells, and blood) clean up dead microbes, cells, and debris. debris.

Fever:Fever:

Non specific defense: Pathogen stimulatesNon specific defense: Pathogen stimulates

lymphocytes to proliferate and secrete a lymphocytes to proliferate and secrete a substance called interleukin-1 (IL-1).substance called interleukin-1 (IL-1).

- endogenous pyrogen- endogenous pyrogen

IL-1 stimulates the hypothalamus to IL-1 stimulates the hypothalamus to increase body temp.increase body temp.

Increased body temp. causes the spleen and Increased body temp. causes the spleen and liver to hold Fe (sequester). Fe level drops liver to hold Fe (sequester). Fe level drops in blood. Since pathogens rely on Fe at in blood. Since pathogens rely on Fe at higher temps to reproduce, this situation higher temps to reproduce, this situation will slow down or stop their growth and will slow down or stop their growth and reproductive cycles.reproductive cycles.