BIO 201 Lecture Exam 2

Lymphatic, Immune, & Respiratory Systems

Immunity

set of diverse processes that protect the body from both cellular injury and disease-causing cells and molecules (pathogens)

Pathogen

anything that causes disease in cells

Lymphatic & Immune Systems…

…Work together

Cellular (Living) Pathogens

• Parasites (ex. tapeworm)

• Protozoa (ex. malaria)

• Fungi (ex. Athlete’s foot)

• Prokaryote (Bacteria; ex. leprosy)

Acellular (Non-Living) Pathogens

• VIirus (ex. HIV)

• Prion (ex. CJD)

Immune System

Function

• Works to defend the body against internal and external threats

Characteristics

• Contains no organs or tissues

  • Consists of cells and proteins located in the blood and tissues of other systems

    • Including the lymphatic system

  • Includes formed elements known as leukocytes, or white blood cells (WBCs), and immune proteins located in the plasma

Lymphatic System

Functions

• Group of organs and tissues that work with the immune system

• Participate in several functions

  • 1. Regulate the volume of interstitial fluid (body tissue fluid)

  • 2. Absorption of dietary fats

  • 3. Immune Functions

Two Main Components:

• Lymphatic Vessels

  • System of blind-ended tubes

• Lymphatic Tissue and Organs

  • Clusters of lymphoid follicles

    • Ex. Mucosa-associated lymphatic tissue (MALT)

      • Tonsils, Peyer’s patches, and appendix

  • Lymph nodes, spleen, and thymus

Regulating the volume of interstitial fluid

One of the main functions of the lymphatic system

• Net filtration pressure (NFP) in blood capillaries favors filtration over reabsorption

  • Overall: more water exits capillaries and enters body tissues

  • Results in an overall loss of water from blood plasma to interstitial fluid

    • About 2-4 liters per day

• Lymphatic vessels pick up fluid and return to circulation

  • Pick up excess fluid in extracellular space, transport it through the body, and deliver it back to the cardiovascular system

Factors of Fluid Loss

• Colloid osmotic pressure pulls water into blood vessels

  • Blood is rich in protein (especially albumin)

• Hydrostatic pressure is great in the arterioles —> pushes water out

• Pressure is reduced in the venule, so there is some inward flow

Net Effect is Fluid Loss

Lymph

Fluid that enters the lymphatic vessels from the extracellular space

• Similar in composition to interstitial fluid

  • Watery, white-ish, sometimes pale yellow

• Sometimes contains cell debris, pathogens, or cancer cells

Absorption of Dietary Fats

One of the main functions of the lymphatic system

• Break down products of fats in the diet that are too large to pass between the endothelial cells of blood capillaries

  • Dietary fats instead enter small lymphatic vessels in the small intestine

  • Travel through lymphatic vessels and are delivered to the blood with lymph

Immune Functions of the Lymphatic System

The lymphatic system plays an important role in protecting the body from infection.

• Lymphoid organs filter pathogens from lymph and blood

  • House several types of leukocytes

    • Plays a role in their maturation

  • The lymphatic system helps to create a memory of specific pathogens that the body has encountered before

Lymphatic Capillaries

Lymphatic vessels begin in tissues with tiny capillaries

• Form a web-like network that surrounds blood capillary beds

• Differ in structure & function from blood capillaries

  • Blind-Ended

    • Lymphatic vasculature is a one-way system that only moves lymph away from other tissues

      • Let things leak into them but not out

  • Valve-like cells of lymphatic capillaries

    • Allow cells such as macrophages and other immune cells to enter lymph

Cells of Lymphatic Capillary Walls

These cells are able to open and close (valve-like)

Increase in Interstitial Fluid Pressure

• Forces lymphatic endothelial cells apart

• Allows large volumes of fluid to enter, but not exit, lymphatic capillaries

Decrease in Interstitial Fluid Pressure

• Endothelial cells flap shut

Metastasis Clinical Connection

• Wandering cancerous cells establish secondary tumors

  • Develop in other locations in the body

• Cancerous cells break free from the primary tumor

• Transported in the lymph

• End up in the Brain, Bones, Liver, and Lungs!

Lymph Nodes

Small, vaguely bean-shaped clusters of lymphatic tissue located along lymphatic vessels throughout the body

• Limit the spread of pathogens through the body by acting as filters.

  • Trap pathogens and prevent them from traveling elsewhere

• Specific clusters include:

  • Axillary Lymph nodes (in axillae, under armpit)

  • Cervical Lymph nodes (in neck)

  • Inguinal Lymph nodes (in the groin)

  • Mesenteric Lymph nodes (in abdominal cavity)

• Normally, they are small and barely distinguishable

  • Become swollen when inflamed

Lymphatic Vessels

• Fed by lymphatic capillaries

• Located adjacent to arteries and veins

• Have valves to prevent pooling and backflow of lymph

• Lymphatic system lacks a pump; moves lymph using:

  • Skeletal muscles and respiratory pumps

  • Pulsatile movement of blood in nearby arteries

  • Rhythmic contraction of smooth muscle in larger lymph vessel walls

Lymphatic Trunks

Interstitial fluid drained into these

• Fed by lymphatic vessels

• Located in many different locations of the body

  • Jugular Trunks

  • Subclavian Trunks

  • Bronchomediastinal Trunks

  • Intestinal Trunks

  • Lumbar Trunks

Jugular Trunks

• Left and right lymphatic trunks that run along the jugular veins

• Drain lymph from the head and neck

Subclavian Trunks

• Left and right lymphatic trunks that run along the subclavian arteries & veins

• Drain lymph from the upper limbs, breasts, and superficial thoracic wall

Bronchomediastinal Trunks

• Left and right lymphatic trunks that run along the area of the lungs and mediastinum

• Drain lymph from deep thoracic structures

Intestinal Trunk

• Lymphatic trunk located around the intestines

• Drain lymph from most abdominal structures

Lumbar Trunks

• Left and right lymphatic trunks located in the lumbar region

• Drain lymph from the lower limbs, abdominopelvic wall, and pelvic organs

Cisterna Chyli

large swollen vessel in which the intestinal trunk and lumbar trunks drain into

• Drains into the thoracic lymphatic duct

Thoracic Duct

drains lymph from the cisterna chyli and trunks from the left side of the body

• Drains all of the lower body and left side of upper body

• Largest lymphatic duct

• Runs along anterior vertebral column from diaphragm to junction of the left subclavian and left jugular veins

Right Lymphatic Duct

remaining lymphatic trunks drain into this tiny duct located near the right clavicle

• Right Jugular Trunk, Right Subclavian Duct, Right Bronchomediatinal Trunk

• Drains into junction of right internal jugular and right subclavian veins

• Drains upper right side of body

Lymphedema

Accumulation of interstitial fluid due to interference with lymphatic drainage

• Causes swelling and pain in the affected area

  • Usually the legs due to gravity

• May interfere with wound healing and contribute to infection

• Mostly caused by blockage of lymph vessels

  • Ex. trauma or infection of lymph vessels or tumors

• Controlled with compression garments, exercise, and massage

• Extreme cases known as elephantiasis

  • Caused by infection of parasitic worms

Reticular Tissue (Lymphoid Tissue)

Loose connective tissue that is the predominant tissue type of the lymphatic system

• Contains specialized cells and thin reticular fibers

• Interweave to form “nets” that trap disease-causing pathogens

• Found in lymphoid organs and also as independent clusters

Cells of Most Lymphoid Organs & Tissues

• Leukocytes:

  • Macrophages (mature monocytes)

  • B and T lymphocytes

• Dendritic Cells

• Reticular Cells

Dendritic Cells

Immune cells with spiny processes resembling dendrites of neurons.

• Originate in the bone marrow or connective tissue

• Responsible for moving fluid around

Reticular Cells

Abundant cells in organs such as the spleen and lymph nodes

• Modified fibroblasts (fiber-forming cells)

• Produce reticular fibers

  • Help anchor lymph tissue in place

Lymphoid Nodules

Clusters of lymphoid cells with some extracellular matrix

• Not entirely surrounded by a connective tissue capsule

• Scattered around the body

  • Found in every body organ

• Help defend against infection

• In some areas, group together to form larger structures

  • Example: MALT

Mucosa-Associated Lymphatic Tissue (MALT)

• Located in areas that are regularly exposed to large amounts of pathogens

  • Gastrointestinal Tracts

  • Respiratory Tracts

  • Genitals

  • Urinary Tracts

  • Oral & Nasal Cavities

• Found in the lamina propria of the mucosa

• Help defend against foreign substances

  • Chief cells can help

Specialized MALT Found in Three Locations of the GI Tract

• Tonsils - located around oral and nasal cavities

• Peyer’s Patches (aggregated lymphoid nodules) - located in the last portion of the small intestine (aka ileum)

• Appendix - protrudes from large intestines

Three Main Tonsils

• Pharyngeal Tonsil (adenoid) - located in posterior nasal cavity (nasopharynx)

• Palatine Tonsils - in posterolateral oral cavity

• Lingual Tonsil - at the base of the tongue

Tonsillar Crypts

Epithelium lining tonsils indents deeply in several locations

• Trap bacteria and debris

• Tonsil location puts them into contact with a large number of potential pathogens

  • Commonly become inflamed when they trap too much

    • Tonsilitis

Peyer’s Patches

defend against any bacteria that have escaped from the large intestine

Appendix

Part of the cecum defends the body from bacteria in the large intestine, specifically those that could be pathogenic

• In plant-eating animals

  • Houses bacteria that can be useful for digesting tough plant fibers

Lymph Node Components

• Afferent Lymphatic Vessels

  • Bring lymph into node

• Efferent Vessels

  • Drains lymph node

  • Located at the hilum (involved portion of node)

• Dense connective tissue capsule encloses node

  • Trabeculae of capsule subdivide node into compartments

• Outer cortex, inner medulla

Cortex of Lymph Nodes

• Contains lymphoid nodules

  • Reticular fibers support a germinal center

    • Houses proliferating B lymphocytes and some macrophages

    • Surrounding mantle zone contains T lymphocytes, macrophages, and dendritic cells

  • Cortical sinuses are tiny open channels limited by macrophages ppo33333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333