Physiology of the Blood I. Fluid compartments and the plasma

Prof. Szabolcs Kéri

University of Szeged, Faculty of Medicine, Department of Physiology

2021

Introductory case vignette

• Young male patient

• Pale skin

• Fatigue, dizziness, shortness of breath

• Poor attention and concentration

• Recurrent infections, fever

• Sensitive gingiva (bleeding)

• Small suffusions under the skin

Blood sample

Increased number of undifferentiated white blood cells

(accelerated division, poor differentiation – lymphoblasts)

Lymphoblasts destroy the bone marrow:

- Red blood cell ↓ → pale skin, fatigue

- Mature white blood cells ↓ → infections

- Platelets ↓ → bleeding

Diagnosis: acute leukaemia

• Blood and the fluid compartments of the body

• Functions of the blood in general

• Components of the blood: plasma and cells

• Anorganic and organic components of the plasma

• Special emphasis: proteins of the plasma

Topics to be discussed:

Intracellular Extracellular

Cell membrane Capillary

wall

Interstitial

fulid Pla

sm

a

Principles of:

- Isotonicty

- Isovolemia

EDEMA: fluid movement and accumulation through the cell membrane and/or capillary wall

Inside the cell

Organization of the fluid spaces: the three-compartment model

Blood and the fluid compartments of the body

Total water: 0.6 x body weight (kg)

1. INTRACELLULAR COMPARTMENT: 0.4 x body weight

2. EXTRACELLULAR COMPARTMENT: 0.2 x body weight

2.1. Interstitial (0.75 x extracellular)

2.2. Intravasal = BLOOD PLASMA (0.25 x extracellular)

2.3. Transcellular (liquor, eye, inner ear, pleura)

Volume = amount of indicator / concentration after equilibrium

- Intravasal: Evans-blue or 131I bound to albumin

- Extracellular: inulin

- Total: tritiated water, antipyrine

When the continuity of fluid compartments is disrupted:thrombosis

Thrombus in the blood vessel

Ahead the thrombus: insufficient/ceased flowBeyond the thrombus: congestion and

edema

Ultrasound diagnosis of deep vein thrombosis

Excessive fluid in the chest: hydrothorax

Chest X-ray:

pleural effusion

(accumulation of fluid around the lungs)

Blood components after centrifugation

PLASMA (55%)

WHITE BLOOD CELLS AND PLATELETS (<1%) (buffy coat)

RED BLOOD CELLS (45%)

HEMATOCRIT: the proportion of cells in the blood (~ 0.44-0.46 male, 0.41-0.43 female)

Sera = plasma without protein fibrinogen (after blood coagulation)

~ 5 liters

Components of the plasma

1. ANORGANIC ELECTROLITES: sodium, potassium, calcium, magnesium,

chloride, bicarbonate, phosphate

2. ORGANIC SUBSTANCES:

- proteins

- glucose

- amino acids

- urea (blood urea nitrogen [BUN]), creatinine, uric acid

- lipids (triglyceride, cholesterol)

- organic acid (lactate, pyruvate, citrate, bilirubin)

Proteins of the plasma

- Synthesis: liver, gut, white blood cells, endothelium (60-80 g/l)

- Function: oncotic pressure, transport, acid-base buffer, inhibition of renal filter and

receptor effect

1. Albumin (35-45 g/l): oncotic pressure, bilirubin transport, binding of drugs

2. α1-globulin: thyroxine, cortisol, vitamin D transport

3. α2-globulin: ceruloplasmin (copper), haptoglobin

4. β-globulin: transferrin (iron)

5. γ-globulin: antibodies

6. Fibrinogen: blood coagulation

Normal Liver cirrhosis

Nephrosis Multiple myeloma

Lipoproteins of the plasma

Hydrophobic core: triglycerides (T), cholesterol (C)

Hydrophilic periphery: phospholipids, apolipoproteins (Apo)

Chylomicron, VLDL (Very Low Density Lipoprotein), IDL (intermediary),

LDL (low), HDL (high): increased density and protein content in this order

Chylo: absorbed from instestines

HDL („good” cholesterol): synthesis in liver, taking up cholesterol in vessels

Peroxisome proliferator

- activated receptors

(PPARs): nuclear receptors,

Apo-expression

Ligand: e.g. fatty acids