Cardiovascular & lymphatic systems Flashcards
Cardiovascular system: components and function
Components
- Blood, heart and blood vessels
Function
- Blood pumped through vessels via the heart
- Oxygen and nutrients carried to cells via the blood.
- Carbon dioxide and waste carried away from cells via blood
- Aids in the regulation of
- acid/base balance
- Temperature
- water content of body fluids
- blood components help defend against disease and repair damaged blood vessels.
Location of the heart
- In the anterior aspect of the thoracic cavity
- Posterior to the sternum
- Normally slightly towards the left
- middle mediastinum a subdivision of the inferior mediastinum.
- Located between the pleural membrane of the left and right lung
- Superior to the diaphragm
Chambers of the heart
-Right atrium
-left atrium
-right ventricle
-left ventricle
-septum
Left ventricle has much larger muscle- thicker muscles indicate strength, it is responsible for pumping blood around the body (systemic circulation).
Right responsible for lungs (pulmonary circulation).
cardiac valves
-pulmonary arteries
-tricuspid valve
-aortic valve
-bicuspid valve
-left ventricular outflow tract
Systematic and pulmonary circulation process
1) deoxygenated blood returns from the body in the vena cava and enters the right atrium.
2) the blood then passes via atrioventricular valve (tricuspid) into the right ventricle and out, via semilunar valve, into the pulmonary artery.
3) The blood now passes through the lungs and returns to the left atrium via the pulmonary vein.
4) the blood passes through a second AV valve (bicuspid) into left ventricle and then through semi lunar valve into the aorta and then body tissues.
Functions of circulatory system
- deliver nutrients and oxygen to tissues
- remove waste products of cellular metabolism (e.g.CO2)
- transport hormones & drugs
- acid base balance
- blood clotting (haemostasis)
- distribution of heat
- immune response
Describe the aorta
- oxygenated blood from the heart is distributed from the aorta to all parts of the body
- systemic circulation
- divided into ascending aorta, aortic arch and descending aorta.
- large diameter, relatively thin walled and highly elastic
- stretches to receive ejected blood from left ventricle
describe the Arteries
- often called distributing arteries
- relatively greater amount of smooth muscle with some elastic fibres
- transport blood over long distances with little drop in blood pressure
- take blood away from the heart
Arterioles
- transition between artery and capillary
- thick muscular wall
- regulate blood flow within tissues
- important role in regulation of arterial blood pressure (called resistance vessels)
Capillariesries:
- form interweaving networks called capillary beds
- microscopic vessels
- form large cross sectional area (13.57 m2)
- exceedingly thin consisting only of tunica intima - single endothelial cell.
- site for diffusion of solutes
Veins
- relatively thin walled with large lumen
- largely non-muscular and elastic
- very distensible and easily collapse
- low pressure vessels
- capacitance vessels: 67% of blood volume contained in veins (Berne & Levy 1998)
- take blood to the heart
Venules
- are the smallest veins
- located at the convergence of capillaries and return blood to veins
Lymphatic and immune system: components and functions
Components
- Lymphatic fluid and vessels;
- Spleen, thymus, lymph nodes and tonsils
Function
- Returns proteins and fluid to blood;
- carries lipids from gastrointestinal tract to blood;
- includes structures where lymphocytes mature and proliferate.
Functions
Immunity
- Production and maturation of white blood cells (lymphocytes and macrophages)
- 90% of immune cells within lymphatic tissue
- Organs/tissue supported by network of vessels
Tissue drainage (homeostasis)
- 21 litres of interstitial fluid diffuses from bloodstream each day
- Most returns to bloodstream directly
- Excess fluid (3-4 litres) drained through lymphatic system
- Maintains pressure and volume of interstitial fluid and blood
Absorption of fat/fat-soluble nutrients/fatty acids
- Into central lymphatic vessels (lacteals) in villi of small bowel
Interstitial fluid and Lymph- Overview
- Interstitial fluid in extra-cellular matrix between cells diffuses freely from bloodstream through permeable capillary walls
- Most diffuses back into bloodstream through venous capillaries
- Remaining fluid diffuses through more permeable lymph capillaries; called lymph
- Passes through lymph vessels though lymph nodes before diffusing back into blood
- Low pressure system parallel (but separate to blood circulation)
- Follows pressure gradient; High in blood capillaries, Low in large veins where terminates
Organs/components in the lymphatic system
- Lymph
- Lymph vessels
- Lymph nodes
- lymph organs: Spleen, thymus
- Diffuse lymphoid tissue: Mucosa-associated lymphoid tissue (MALT) – Tonsils, Gut-associated lymphoid tissue (GALT) PEYER’S PATCHES
- Bone marrow
Lymph capillaries
- Similar to blood capillaries; single layer of endothelial cells
- More permeable; proteins, cell debris etc
Designed to let fluid only flow one way: - Closed at proximal end (start)
- Overlapping epithelium Designed to let fluid in but not out act as one way valves under pressure
- Start as tubes in interstitial spaces, join together to form larger lymph vessels
- Form a network of lymph drainage throughout body
Lymphatic vessels
- Formed by network of lymphatic capillaries
- Usually follow vascular network
Similar in structure to small veins:
- Thin walls;
- Cup-shaped Valves to prevent backflow
- Low pressure
Movement of lymph (similar to venous return) via:
- rhythmic contraction of muscle layer causes lymph movement
- Contraction of adjacent muscles and pulsating arteries
Lymphatic ducts
- Lymphatic vessels drain into two large ducts
- Both drain back into venous system through respective subclavian veins
Thoracic duct
- Drains the majority of the body: legs, pelvis and abdomen, left arm, left side of thorax, head and neck
Right lymphatic duct
- Drains right arm and right side of head, neck, and thorax
Lymph nodes
- Small oval/bean-shaped organs along length of lymph vessels, usually in groups
- Lymph normally passes through a number (8-10) of nodes before re-entering the circulation
- Vary in size from 1mm to 20mm
Functions are: - Filtration and phagocytosis
- Proliferation (multiplication) of lymphocytes; when activated they release antibodies
Lymphatic organs
Primary
- Sites of lymphocyte development
- Bone marrow
- thymus
Secondary
- Reservoirs (storage) of lymphocytes
- Sites of immune response
- Lymph nodes
- Spleen
- Mucosa-associated lymphoid tissue MALT
The spleen
- Largest lymphatic organ
- Like lymph nodes; comprised of reticular (structure) and lymphatic tissue and surrounding by fibrous capsule with trabeculae
- Left hypochondriac region between left hemi diaphragm and fundus of stomach
- Contains lymphocytes and macrophages.
- Destroys blood cells that are old
- Stores blood
Thymus
- Lies in superior mediastinum/root of neck, posterior to sternum and between lungs
- Grows from birth until puberty. Then atrophies back to original birth size by middle age
- Surrounded by fibrous capsule which, like lymph node and spleen, extends into body and forms lobules
- Contain large amount of lymphocytes
- Key to developing immunity
Diffuse lymphoid tissue
- Concentrations of lymphatic tissue not surrounded by fibrous capsule
- Scattered in connective tissue of mucous membranes; strategic places
- Contain b- and t-lymphocytes from bone marrow/thymus
- Early sites of defence against infection
- Has no afferent lymph vessels – not affected by disease spread by lymph
- Mucosa-associated lymphoid tissue (malt): Tonsils
- Gut-associated lymphatic tissue (galt): PEYER’S PATCHES/AGGREGATED LYMPHOID FOLLICLES IN SMALL BOWEL, APPENDIX
What are the 3 types of blood cells and what are blood cells?
- Three main types of blood cell:
*Red cells (erythrocytes)
*Platelets (thrombocytes)
*Leukocytes (white cells) - originate from pluripotent stem cells (can develop into a number of different cells)
- Process called haematopoiesis
- Mostly in the red bone marrow, some types of leukocytes develop in lymphoid tissue (lymphocytes)
- Red marrow in all bones at birth; in adults only in flat bones, irregular bones, and ends of long bones; Replaced by fatty yellow bone marrow (no haematopoiesis)
