1) Storage - the stomach allows a meal to be consumed and the materials released incrementally into the duodenum for digestion. It may take up to four hours for food from a complete meal to clear the stomach. 
2) Chemical digestion - pepsin begins the process of protein digestion cleaving large polypeptides into shorter chains . 
3) Mechanical digestion - the churning action of the muscularis causes liquefaction and mixing of the contents to produce acid chyme. 
4) Some absorption - water, electrolytes, monosaccharides, and fat soluble molecules including alcohol are all absorbed in the stomach to some degree.

Hyperventilation

1. Treatments :Rebreath air, hold breath (Increase CO₂)
   Give oxygen for Hypoxemia

The small intestine

Digestion within the small intestine produces a mixture of disaccharides, peptides, fatty acids, and monoglycerides. The final digestion and absorption of these substances occurs in the villi, which line the inner surface of the small intestine.

This scanning electron micrograph (courtesy of Keith R. Porter) shows the villi carpeting the inner surface of the small intestine.

The crypts at the base of the villi contain stem cells that continuously divide by mitosis producing

• more stem cells
• cells that migrate up the surface of the villus while differentiating into
  1. columnar epithelial cells (the majority). They are responsible for digestion and absorption.
  2. goblet cells, which secrete mucus;
  3. endocrine cells, which secrete a variety of hormones;
• Paneth cells, which secrete antimicrobial peptides that sterilize the contents of the intestine.

All of these cells replace older cells that continuously die by apoptosis.

The villi increase the surface area of the small intestine to many times what it would be if it were simply a tube with smooth walls. In addition, the apical (exposed) surface of the epithelial cells of each villus is covered with microvilli (also known as a "brush border"). Thanks largely to these, the total surface area of the intestine is almost 200 square meters, about the size of the singles area of a tennis court and some 100 times the surface area of the exterior of the body.

Incorporated in the plasma membrane of the microvilli are a number of enzymes that complete digestion:

• aminopeptidases attack the amino terminal (N-terminal) of peptides producing amino acids.
• disaccharidasesThese enzymes convert disaccharides into their monosaccharide subunits.
  • maltase hydrolyzes maltose into glucose.
  • sucrase hydrolyzes sucrose (common table sugar) into glucose and fructose.
  • lactase hydrolyzes lactose (milk sugar) into glucose and galactose.

Fructose simply diffuses into the villi, but both glucose and galactose are absorbed by active transport.

• fatty acids and monoglycerides. These become resynthesized into fats as they enter the cells of the villus. The resulting small droplets of fat are then discharged by exocytosis into the lymph vessels, called lacteals, draining the villi.

Alveolar Ventilation: is the volume of air of new air , entering the alveoli and adjacent gas exchange areas each minute . It equals to multiplying of respiratory rate by ( tidal volume - dead space).
Va = R rate X (TV- DsV)
     = 12 X ( 500-150)
     = 4200 ml of air.

Blood Transfusions

• Some of these units ("whole blood") were transfused directly into patients (e.g., to replace blood lost by trauma or during surgery).
• Most were further fractionated into components, including:
  • RBCs. When refrigerated these can be used for up to 42 days.
  • platelets. These must be stored at room temperature and thus can be saved for only 5 days.
  • plasma. This can be frozen and stored for up to a year.

safety of donated blood

A variety of infectious agents can be present in blood.

• viruses (e.g., HIV-1, hepatitis B and C, HTLV, West Nile virus
• bacteria like the spirochete of syphilis
• protozoans like the agents of malaria and babesiosis
• prions (e.g., the agent of variant Crueutzfeldt-Jakob disease)

and could be transmitted to recipients. To minimize these risks,

• donors are questioned about their possible exposure to these agents;
• each unit of blood is tested for a variety of infectious agents.

Most of these tests are performed with enzyme immunoassays (EIA) and detect antibodies against the agents. blood is now also checked for the presence of the RNA of these RNA viruses:

• HIV-1
• hepatitis C
• West Nile virus

• by the so-called nucleic acid-amplification test (NAT).

Bleeding Disorders

A deficiency of a clotting factor can lead to uncontrolled bleeding.

The deficiency may arise because

• not enough of the factor is produced or
• a mutant version of the factor fails to perform properly.

Examples:

• von Willebrand disease (the most common)
• hemophilia A for factor 8 deficiency
• hemophilia B for factor 9 deficiency.
• hemophilia C for factor 11 deficiency

In some cases of von Willebrand disease, either a deficient level or a mutant version of the factor eliminates its protective effect on factor 8. The resulting low level of factor 8 mimics hemophilia A.