anatomy exam 4

what is the primary function of the lymphatic system?

production and distribution of lymphocytes that provide defense against infections and environmental hazards

lymphatic capillaries

closed-ended vessels; in SI, called lacteals

how does fluid move in lymphatic vessels?

epithelial cells in wall overlap and act like one-way valves: fluid carries viruses and bacteria; fluid moves in (not out!)

what do lymphatic vessels carry?

lymph- basically same as plasma and interstitial fluid (includes lipids absorbed by GI tract)

what do lymphatic vessels drain into?

larger and larger lymphatic vessels

what allows for movement of lymph through lymphatic vessels?

have valves and skeletal muscle contraction allows for movement of lymph

what does lymph flow through along interval of the lymphatic vessels?

lymph nodes

where does most lymph eventually flow to?

the thoracic duct

the thoracic duct

lies along anterior surface of thoracic vertebral bodies; empties into L subclavian vein

what drains lymph from most of the body?

thoracic duct

types of lymphocytes:

T (thymus dependent) cells, B (bone marrow) cells, and NK (natural killer) cells

T cells

formed in bone marrow, and mature in the thymus. subtypes include:

• cytotoxic T cells (aka killer T)- attack foreign cells or body cells infected by viruses

• helper T cells- stimulate T and B cells

• suppressor T cells- inhibit T and B cells

• memory T cells

which cells control the sensitivity of the immune response

helper T cells and suppressor T cells

B (bone marrow derived) cells

form and mature in the bone marrow

can differentiate into plasma cells, which produce antibodies (immunoglobins -IG’s)

life span of lymphocytes?

4-20 years

what is the process of lympocytes being made?

lymphopoiesis

lymphoid tissues

nodules and tonsils

nodules

clusters of lymphoid tissue occur deep to epithelial lining of respiratory, urinary, and digestive tracts, includes appendix

tonsils (what are they/what are the various types?)

large nodules in oral and nasal cavities → attack if a foreign substance is inhaled or ingested

• pharyngeal tonsils (adenoids) - nasal pharynx

• palatine tonsils - on sides of soft palate

• lingual tonsils - at base of tongue

lymphoid organs

nodes, thymus gland, spleen

nodes

1-25mm (about an inch)

distributed throughout body, but some are grouped together: axillary, cervical, inguinal

What is the make up of nodes

largely consists of B cells and plasma cells

how does lymph move through nodes/vessels?

lymph moves through vessels and filters through nodes along the way → foreign substances are trapped in the node and destroyed by lymphocytes and macrophages

what do swollen glands indicate?

inflammation/infection due to an increase in the number of lymphocytes in nodes

how do cancer cells spread through out the body?

they can travel through the lymphatic system - metastasize and produce clusters of tumor cells in nodes along the way → further spread

thymus gland

just deep to the sternum

how does the thymus gland develop throughout life?

very large during infancy and childhood → decreases in size as we age → replaced with adipose and CT just after puberty

spleen (size and location)

largest mass of lymphatic tissue (12cm/5inch)

L of stomach and between ribs 9-11

what makes up the spleen?

contains white pulp and red pulp

• white pulp - mostly lymphocytes

• red pulp - venous sinuses - similar to vv (filled with blood)

function of spleen?

blood filtered and phagocytosis of bacteria and worn out blood components

initiates immune response by B cells and T cells

structure of spleen

very soft, if damaged → internal bleeding

innate defenses

born with these → physical barriers, phagocytes, immunological surveillance, interferons

innate defenses - physical barriers

skin, mucus membranes, and hair

what are examples of the skin and mucus membranes providing an innate defense for the body?

skin + mucus membranes = tightly packed cells

• produce sweat, oils, and/or mucus - trap and/or wash away microbes

• stomach mucosa produces HCl and enzymes - destroy bacteria

types of phagocytes?

neutrophils, eosinophils, fixed macrophages, free macrophages

movement of neutrophils and eosinophils?

circulate in blood

fixed vs free macrophages

fixed- stationary in many body tissues, esp. CT

free- travel throughout body to injury sites

describe the immunological surveillance of innate defenses

constant monitoring of normal tissues by NK cells

1. respond immediately and recognize abnormal antigens (Ags) on surface of abnormal cell

2. produce perforins, which ‘poke holes’ in PM of abnormal cell → cell death

describe interferons of innate defenses

infected cells (virus) produce interferons → bind to uninfected cells → stimulate them to produce antiviral proteins

describe the connections in the circle of willis

vertebral a → basilar a → posterior cerebral a

internal carotid a → middle cerebral + anterior cerebral a

*posterior communicating connects posterior cerebral to internal carotid

*anterior communicating connects left and right anterior cerebral a

what is the circle of willis formed from?

basilar and internal carotid aa

how does blood flow through the circle of willis?

anterior circulation: from the internal carotid aa → middle cerebral aa + anterior cerebral aa

posterior circulation: from vertebral aa → basilar a → posterior cerebral aa

**very little blood flow thru communicating aa under normal conditions, but if there’s a blockage or narrowing of aa, then blood is redistributed through the anterior and posterior communicating aa to maintain cerebral perfusion

**flow is dependent on pressure

dural sinus role

between layers of dura mater, drain deoxygenated blood from the brain, direct everything toward internal jugular veins

no valves

flow of blood through the dural sinuses

venous blood from the brain drains into the superior and inferior sagittal sinus

inferior sagittal sinus → straight sinus

straight sinus + superior sagittal sinus converge at the confluence of sinuses

→ transverse sinus → sigmoid sinus

exits skull thru jugular foramen → internal jugular vein

meninges

dura mater + arachnoid + pia mater

dura mater

falx cerebri + falx cerebelli + tentorium cerebelli

dural sinuses surround these