Physiology of the Blood I. The plasma and fluid compartments

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