Blood and Body Fluids

Cardiac muscle: note the branching nature of the cardiac muscle fibres

The Blood Vessels

White blood cell (granular) Red Blood Cells The Reds and The Whites

The level of salt in plasma is about equal to that of sea water. In an average healthy person, approximately 45 per cent of the blood volume is cells, among them red cells (the majority), white cells, and platelets. A clear, yellowish fluid called plasma makes up the rest of blood. Plasma, 95 per cent of which is water, also contains nutrients such as glucose, fats, proteins, and the amino acids needed for protein synthesis, vitamins, and minerals.

Plasma and Tissue Fluid Recirculation As we have just seen, the pale yellow liquid known as plasma contains: Water (95%!) Nutrients (Can you name the main one?) Waste (And what’s this called?) Plasma proteins Cells (The Reds and The Whites) What are ALBUMINS? Where do they go?

So what is tissue fluid? Blood enters capillaries at HIGH PRESSURE Plasma is forced out of the capillaries through gaps between the capillary endothelial cells Plasma proteins and red blood cells DO NOT pass through. Look at this table and try to work out why they don’t pass out of the capillaries: Substance Relative Molecular Mass water 18 glucose 180 Haemoglobin Albumin 69000

If fluid passes out of the capillaries into the tissues, how does it re-enter the circulatory system? Plasma protein concentration at the venous end of capillaries is HIGH. Osmotic pressure draws fluid back into the capillary This system accounts for 90% of the tissue fluid returned into the circulation. What happens to the other 10%?

Another system of vessels exists in the body! The smallest branches of these vessels lie in the body tissues and ‘collect’ fluid: Lymph vessels or lymphatics The fluid is called LYMPH and contains proteins which have originated from the tissues themselves The lymphatics ‘empty’ into branches of the vena cava (called the subclavian veins)……….so the remaining 10% of fluid finds its way back into the circulation!

Why does tissue fluid (and therefore lymph) vary from one part of the body to another? Compare the tissue fluid around liver cells and around intestinal villi…….What do you think that you will find? Flow of lymph depends on contraction of muscle around the vessels. Lymph vessels also have valves. Why? Why is lymph flow MASSIVELY SLOWER than blood flow in the body?

Policing of Tissues The circulation of blood, tissue fluid and lymph allows the whole body to be continually checked for invaders In addition to patrolling surveillance, there are specific ‘checkpoints’, the LYMPH NODES

WBCs are larger than Red Blood Cells There are fewer WBCs than RBCs, about one white for every 600 red Their main job is to protect the body against infection Like RBCs, they are made in the bone marrow Unlike RBCs, they contain a central nucleus and many can change shape There are several kinds of WBCs White Blood Cells: The Facts

White blood cells are known as LEUCOCYTES ( lew-ko-sites )

Broadly speaking, they can be divided into two categories: PHAGOCYTES Destroy invading microorganisms by phagocytosis Recognised by granular cytoplasm and lobed nuclei LYMPHOCYTES Smaller than phagocytes Large round nucleus Only small amount of cytoplasm Destroy invaders by producing antibodies or by killing invaders directly.

The Phagocytes……. 1.Neutrophils: Form about 60% of all WBCs. Patrol the circulation and the tissues by squeezing out of capillaries. Released in large numbers during an infection. Short lived. 2. Eosinophils: Respond to parasitic infections and allergic conditions 3. Monocytes: The precursors for macrophages. Once circulating monocytes enter tissues, they are converted into macrophages. Macrophages break up invaders to expose antigens to lymphocytes.

If the body is wounded, white blood cells pass through the walls of blood vessels where they attack and engulf invading bacteria White Blood Cell

The Lymphocytes…….. Each type is specialised to respond to one antigen. Circulate throughout blood and lymph, so come into contact with any pathogens and each other. B and T cells interact with each other for effective defence. B Cells: Divide and secrete antibodies into the blood T Cells: Subdivided into T Helper Cells and T Killer Cells: T Helper Cells: Release chemicals which stimulate B Cells T Killer Cells: Attach to diseased cells in the body and release toxin to kill cell and pathogen

White Blood Cells

Platelets Platelets are derived from special blood cells in the bone marrow They help repair torn blood vessels and clot blood following an injury When there is no injury, they circulate in the blood in an ‘inactivated’ state Red blood cell Inactivated platelet

Activated platelets have ‘processes’ which help plug the wound

Red Blood Cells: Revision Biconcave disc 7 micrometres diameter No nucleus No mitochondria Oxygen carried by haemoglobin

Platelet Monocyte T-Lymphocyte Red Blood Cell Can you identify these cells?

Now try and identify these White Blood Cells: (The images have been photographed using a light microscope)

Neutrophil

Lymphocyte Neutrophil

Eosinophil

Neutrophil

Monocyte Neutrophil

Lymphocytes Neutrophils

Basophil Lymphocyte