hs 130 anatomy & physiology ii unit 3 seminar chapter 13 the lymphatic system and immunity
TRANSCRIPT
HS 130 Anatomy & Physiology IIUnit 3 Seminar
Chapter 13The Lymphatic System
And Immunity
•Questions, Problems, Concerns
The Lymphatic System
• Functions of the lymphatic system Allows exchange of substances, such as
excess fluid and protein molecules, that cannot occur in the capillary beds
Filters out harmful substances from the lymph before returning it to the blood
Acts as sewer system of the body
What is the role of lymph nodes in the spread of cancer?
What role do tonsils play in preventing the spread of infection to the lower respiratory tract?
Lymph—fluid in the tissue spaces that carries protein molecules and other substances back to the blood
Lymphatic vessels—permit only one-way movement of lymph Lymphatic capillaries—tiny blind-ended tubes distributed in
tissue spaces Microscopic in size Sheets consisting of one cell layer of simple squamous
epithelium Poor “fit” between adjacent cells results in porous walls Called lacteals in the intestinal wall (fat transportation from
food to bloodstream) Right lymphatic duct
Drains lymph from the right upper extremity and right side of head, neck, and upper torso
Thoracic duct Largest lymphatic vessel Has an enlarged pouch along its course, called cisterna
chyli Drains lymph from about three-fourths of the body
The Lymphatic System
What happens to fluid from blood plasma that is not reabsorbed by blood vessels?
Which lymphatic duct drains most of the body?
What is the function of the cisterna chyli?
What are lacteals?
Lymph nodesFilter lymphLocated in clusters along the pathway
of lymphatic vesselsFunctions include defense and WBC
formationFlow of lymph: to node via several afferent lymph
vessels drained from node by a single
efferent lymph vessel
The Lymphatic System
What is this diagram showing?
• Thymus: Lymphoid tissue organ located in mediastinum Total weight of 35 to 40 g (a little more
than an ounce) Plays a vital and central role in immunity Produces T lymphocytes, or T cells Secretes hormones called thymosins In adults, lymphoid tissue is largely
replaced by fat and connective tissue in the process called involution
The Lymphatic System
What would you expect the course of therapy to be if a baby were born without a thymus gland?
• Tonsils Composed of three masses of lymphoid
tissue around the openings of the mouth and throat Palatine tonsils (“the tonsils”) Pharyngeal tonsils (adenoids) Lingual tonsils
Subject to chronic infection Enlargement of pharyngeal tonsils may
impair breathing
The Lymphatic System
Why would you try to avoid removal of the tonsils if at all possible?
• Spleen Largest lymphoid organ
in body Located in upper left
quadrant of abdomen Often injured by trauma
to abdomen Surgical removal called splenectomy Functions include
phagocytosis of bacteria and old RBCs
acts as a blood reservoir
The Lymphatic System
Often after the surgical removal of a breast, lymph nodes, and lymphatic vessels — especially those in the upper arm — swelling occurs. What is the physiological reason that swelling takes place?
Some surgical treatments for breast cancer involve removal of lymph nodes in the axillary region. Why might this have a therapeutic effect in some cases?
Diseases of the lymphatic system:LymphangitisLymphedemaElephantiasisLymphomaTonsillitisSplenomegaly
• Functions of the immune system Protects the body from pathologic bacteria,
foreign tissue cells, and cancerous cells Made up of specialized cells and molecules
The Immune System
• Nonspecific immunity Skin: Mechanical barrier to bacteria and
other harmful agents Tears and mucus: Wash eyes and trap
and kill bacteria Inflammation
Attracts immune cells to site of injury, increases local blood flow, increases vascular permeability
Promotes movement of WBCs to site of injury or infection
The Immune System
• Inflammatory Response Inflammation is a generalized response to an
invader, such as bacteria that are causing tissue damage
This triggers release of factors from immune cells The presence of immune factors attracts WBCs Factors also cause increased blood flow (site
becomes warm and reddened) and increased vascular permeability (site swells with associated discomfort)
These immune factor-mediated changes help phagocytic WBCs reach the site and enter the affected tissue
The Immune System
Specific immunity Also called adaptive immunity because of the
ability of the body to recognize, respond to, and remember harmful substances or bacteria
Types of specific immunityNatural immunity—exposure to causative
agent is not deliberateActive—active disease produces immunityPassive—immunity passes from mother to
fetus through placenta or from mother to child through mother’s milk
Artificial immunity—exposure to causative agent is deliberateActive—vaccination results in immunityPassive—protective material developed in
another individual’s immune system and given to previously nonimmune individual
The Immune System
• Antibodies: Protein compounds with specific combining sites Combining sites attach antibodies to specific
antigens, forming an antigen–antibody complex Inactivation of foreign protein in this way
is called humoral or antibody-mediated immunity
Antigen–antibody complexes have various modes of action Neutralize toxins Clump or agglutinate enemy cells Promote phagocytosis
The Immune System Molecules
• Complement Proteins Group of at least 14 proteins normally present
in blood in an inactive state Complement fixation
Important mechanism of action for antibodies
Causes cell lysis by permitting entry of water through a defect created in the plasma membrane
• Phagocytes: Ingest and destroy foreign cells or other harmful substances via phagocytosis Types
Neutrophils Monocytes Macrophages
o Kupffer’s cellso Dust cells
The Immune System Molecules
Where do phagocytes and lymphocytes originate?
• Lymphocytes Most numerous of immune system cells Development of B cells
Primitive stem cells migrate from bone marrow and go through two stages of development
The Immune System Molecules
• Development of B Cells Stage 1
Stem cells develop into immature B cellsoImmature B cells are small lymphocytes; each synthesizes highly specific antibody molecules in their plasma membranes
Migrate via the bloodstream chiefly to lymph nodes
Become seed cells in the lymph nodes Undergo mitosis to make clones of
themselves containing their specific antibody
The Immune System Molecules
• Development of B Cells Stage 2
Immature B cell develops into activated B cell if it comes in contact with its specific antigen
B cell is activated by antigens binding to its surface antibodies
Activated B cell divides repeatedly, forming two clones of cells:
o Plasma cells o Memory cells
Slide 31
• Function of B Cells Humoral immunity
Activated B cells develop into plasma cells
Plasma cells secrete antibodies into the blood
Circulating antibodies produce humoral immunity
• Development of T Cells Stage 1
Stem cells from bone marrow migrate to thymus gland
Stem cells develop into T cells several months before and after birth
T cells have protein molecules on their cytoplasmic membrane shaped to bind to only one kind of antigen
T cells migrate from thymus chiefly to lymph nodes, liver, and spleen
Stage 2 Occurs only if a specific antigen binds to T
cells’ surface proteins T cells develop into sensitized T cells
• Functions of T Cells Provide cell-mediated immunity Kill invading cells directly by releasing
a substance that poisons cells Release chemicals that attract and
activate macrophages to kill cells by phagocytosis
What happens when T-cell function is impaired?
• Humoral immunity Immunity conferred by the action of
antibodies Activated B cells plasma cells and
memory cells • Cell-mediated immunity
Immunity conferred by the action of cells Sensitized T cells Kill invading cells directly by releasing
lymphotoxin or releasing lymphokines that attract and activate macrophages to kill cells by phagocytosis
Humoral vs Cell-mediated Immunity
Questions??Remember you can email or IM
any questions or concerns to me
Thanks for attending!!
I’ll “see” everyone on the discussion boards!