Exocrine functions of the pancreas

Each day the pancreas secretes approximately 1 L of alkaline isosmotic pancreatic juice that originates from the pancreatic acinar cells and pancreatic ducts. The colorless, bicarbonate-rich, and protein-rich pancreatic juice plays key roles in duodenal alkalinization and food digestion. The acinar cells secrete the enzymes required for the digestion of the three main food types: amylase for carbohydrate (starch) digestion, proteases (e.g., trypsin) for protein digestion, and lipases for fat digestion. The acinar cells are pyramidal in shape with the apices facing the lumen of the acinus, where the enzyme-containing zymogen granules fuse with the apical cell membrane for release. Acinar cells, unlike the endocrine cells of the pancreas, are not specialized and produce all three types of pancreatic enzymes from the same cell type.

Exocrine functions of the pancreas

Amylase is secreted in its active form and hydrolyzes starch and glycogen to the simple sugars of dextrins and maltose; maltose is then metabolized to glucose by intestinal maltase. 

📖 Transplantation, Bioengineering, and Regeneration of the Endocrine Pancreas: Volume 1  

Portal system

 The portal system is responsible for transporting blood from most of the gastrointestinal tract to the liver for metabolic processing before the blood returns to the heart. The portal system drains venous blood from the distal end of the esophagus, stomach, small and large intestines, proximal portion of the rectum, pancreas, and spleen. The portal system is the venous counterpart to areas supplied by the celiac trunk and the superior and inferior mesenteric arteries.

The portal venous system

The liver is unique in that it receives both nutrient-rich deoxygenated blood (portal vein) and oxygenated blood (hepatic arteries). The portal vein branches as it enters the liver, where its blood percolates around hepatocytes in tiny vascular channels known as sinusoids. Hepatocytes detoxify the blood, metabolize fats, carbohydrates, and drugs, and produce bile. The sinusoids receive deoxygenated blood from the portal veins (provide blood for metabolism and detoxification) and oxygenated blood from the hepatic arteries (provide oxygen for hepatocytes). Blood exits the sinusoids into a central vein, which empties into the hepatic veins and ultimately into the inferior vena cava, which passes through the diaphragm before entering the right atrium of the heart.

Portal vein.

  Oral drugs travel throughout the gastrointestinal tract, where they are absorbed by the small intestine. These drugs then travel to the liver via the hepatic portal system, where they are metabolized before entering the systemic circulation.

📖 Sleisenger and Fordtran’s Gastrointestinal and Liver Disease- 2 Volume Set  

Brachial artery

As a continuation of the axillary artery, it begins at the inferior border of the teres major tendon and it ends at the level of the neck of the radius about 1cm distal to the elbow joint. At this point, it divides into the ulnar and radial arteries. The brachial artery runs medial to the humerus proximally, before moving more anteriorly to lie between the epicondyles of the humerus.

 Brachial artery

Relationships of the brachial artery to other structures in the arm can be important in clinical practice. The brachial artery is a superficial vessel and is only covered by the layers of the skin, as well as the superficial and deep fasciae, with a few exceptions:

The first exception to this is at the cubital fossa, where the bicipital aponeurosis, which is the aponeurosis of the biceps brachii muscle, covers the artery, and separates it from the median cubital vein.

The second exception is when the median nerve crosses the brachial artery near the distal attachment of the coracobrachialis.

 Brachial artery

Posteriorly, the brachial artery is separated from the long head of the triceps brachii muscle by the profunda brachii artery and the radial nerve. The attachments of the coracobrachialis and the brachialis muscles, as well as the medial head of the triceps brachii muscle, also lie posterior to the brachial artery.

The median nerve and coracobrachialis muscle lie laterally to the brachial artery at its proximal aspect whereas the medial cutaneous nerve of the forearm and the ulnar nerve lie medially to the artery proximally.

📖 Clinically Oriented Anatomy 7th Edition  

Kyphoscoliosis

Kyphoscoliosis has long been recognized as a cause of cardiorespiratory failure. Only in recent years, however, has the combination of clinical picture, physiologic measurements, and anatomic observations at autopsy clarified the natural history of the cardiorespiratory disorder.

Kyphoscoliosis

Unless there is independent lung disease, such as bronchitis or emphysema, only patients with severe spinal deformities are candidates for cardiorespiratory failure. Subjects with mild deformities are consistently asymptomatic. In contrast, those with severe degrees of deformity, particularly if considerable dwarfing has occurred, are often restricted in their activities by dyspnea on exertion. They are most prone to cardiorespiratory failure if an upper respiratory infection should supervene. From the point of view of disability and the likelihood of cardiorespiratory failure, the nature of the deformity (i.e., kyphosis, scoliosis, or both) is unimportant when compared with the severity of the deformity and dwarfing.

Kyphoscoliosis in the lower thoracic and lumbar spine. 10-year-old female with rib head dislocation from dystrophic scoliosis. FINDINGS: 3-D reconstructed CT image of the thoracolumbar spine demonstrates a severe Sshaped scoliotic curve in the lower thoracic and lumbar spine. TECHNIQUE: Noncontrast axial CT (100 mAs, 120 kVp, Slice thickness: 2.5 mm). 

One approach to classifying individuals with kyphoscoliosis is on the basis of lung volumes. The more normal the total lung capacity, vital capacity, and tidal volume, the more the subject tends to remain asymptomatic. In those with severe reduction in lung volumes, the stage is set for cor pulmonale.

📖 Campbell’s Operative Orthopaedics, 4-Volume Set 13th Ed  

Tubuloglomerular feedback

   The available evidence suggests that the macula densa, located at the end of the thick ascending limb, senses tubular flow based on the concentrations of sodium and chloride in the local filtrate. The sensing apparatus appears to be apical Na+/K+/2Cl− (NKCC2) cotransporters. 

Tubuloglomerular feedback and modulation of renin release

When tubular fl ow rates are high, there is a slight decrease in solute reabsorption before the macula densa, and thus higher concentrations of sodium and chloride are present at this area. Increased activation of NKCC2 transporters ensues, which leads to   constriction of the afferent arteriole and inhibition of renin release.

📖 Critical Care Nephrology 3rd Edition