IRY CHEMISTRY AND BIOCHEMISTRY lysosomes: capsules of enzymes (usually hydrolytic)distributed fairl uniformly throughout the cytoplasm Fat droplets and vesicles of material for excretion are usually apparent toward the apical region of the cell. The apical membrane possesses microvilli which serve to greatly increase its surface area 1.6 Techniques used to study milk synthesis 1. 6. Arteriovenous concentration differences The arterial and veinous systems supplying the mammary gland( Figure 1 for analysis. Differences in composition between arterial and venous blood give a measure of the constituents used in milk synthesis. The total amount of constituent used may be determined if the blood flow rate is known, which may be easily done by infusing a known volume of cold saline Figure 1.5 The blood vessel and nerve supply in the mammary glands of a cow Circulatory system(arteries, white: veins, stippled ) h, heart; a, abdominal aorta; pa, external pudic artery; Nerves: 1, first lumbar nerve; 2, second lumbar nerve: 3, external sper erve; 4, perineal nerve. A and v show blood sampling points for arteriovenous(Av)difference determinations (Mepham, 1987).a DAIRY CHEMISTRY AND BIOCHEMISTRY 0 lysosomes: capsules of enzymes (usually hydrolytic) distributed fairly uniformly throughout the cytoplasm. Fat droplets and vesicles of material for excretion are usually apparent toward the apical region of the cell. The apical membrane possesses microvilli which serve to greatly increase its surface area. 1.6 Techniques used to study milk synthesis 1.6.1 Arteriovenous concentration diferences The arterial and veinous systems supplying the mammary gland (Figure 1.5) are readily accessible and may be easily cannulated to obtain blood samples for analysis. Differences in composition between arterial and venous blood give a measure of the constituents used in milk synthesis. The total amount of constituent used may be determined if the blood flow rate is known, which may be easily done by infusing a known volume of cold saline Figure 1.5 The blood vessel and nerve supply in the mammary glands of a cow. Circulatory system (arteries, white; veins, stippled): h, heart; a, abdominal aorta; pa, external pudic artery; pv, external pudic vein; s, subcutaneous abdominal vein; c, carotid artery; j, jugular vein. Nerves: 1, first lumbar nerve; 2, second lumbar nerve; 3, external spermatic nerve; 4, perineal nerve. A and V show blood sampling points for arteriovenous (AV) difference determinations (Mepham, 1987)