What happens to blood flow when vascular resistance increases due to vasoconstriction?

A. By suppressing respiratory centers to reduce oxygen consumption: Chemoreceptors do not suppress respiration in response to acidosis. Instead, they activate respiratory centers to increase ventilation, helping to remove carbon dioxide and raise blood pH toward normal. Suppressing respiration would worsen acidemia.

B. By stimulating the cardioinhibitory centers to decrease heart rate: Chemoreceptors primarily influence ventilation and sympathetic outflow rather than directly decreasing heart rate. While extreme hypoxia or hypercapnia can modulate cardiac activity, the immediate response to low pH involves increasing sympathetic drive, not reducing heart rate.

C. By increasing cardiac output and vasoconstriction to enhance circulation: Peripheral chemoreceptors detect low pH (high hydrogen ion concentration) and low oxygen levels, triggering sympathetic activation. This increases cardiac output and causes systemic vasoconstriction, helping maintain perfusion and oxygen delivery to vital organs while ventilation corrects acid-base imbalance.

D. By signaling the kidneys to excrete more hydrogen ions: While the kidneys play a key role in long-term acid-base regulation by excreting hydrogen ions, chemoreceptors act rapidly through the nervous system. Renal compensation is slower and does not constitute the immediate response to a drop in blood pH.

Axillary Artery: C

Left Subclavian Artery: K

Ulnar Artery: F

Superficial Palmar Arch: H

A. Axillary artery: The axillary artery, presented by letter C is the continuation of the subclavian artery. It courses through the axilla and becomes the brachial artery at the inferior border of the teres major muscle. It gives off key branches including the thoracoacromial, lateral thoracic, subscapular, and anterior and posterior circumflex humeral arteries. It supplies the shoulder joint, lateral thoracic wall, and upper limb.

B. Left Subclavian artery: The left subclavian artery presented as K arises from the arch of the aorta, posterior to the left common carotid artery. It travels laterally toward the upper limb, arching over the apex of the lung and passing between the anterior and middle scalene muscles. It supplies blood to the brain (via the vertebral artery), thoracic wall, and left upper extremity.

C. Ulnar artery: The ulnar artery as F is one of the two terminal branches of the brachial artery, arising in the cubital fossa opposite the neck of the radius. It travels along the medial (ulnar) side of the forearm. It primarily forms the superficial palmar arch and supplies the medial forearm, hand muscles, and digits, particularly the medial three and a half fingers.

D. Superficial palmar arch: The superficial palmar arch as H, is an arterial arcade in the palm primarily formed by the ulnar artery, with contribution from the superficial branch of the radial artery. From this arch arise the common palmar digital arteries, which divide into proper digital arteries supplying the fingers, ensuring collateral circulation within the hand.