Tag: busy at work - our internal organs

Actually, only about 350 mL of air (out of total 500 mL tidal volume) enters the lung alveoli for the exchange of gases. The remaining 150 mL fills the respiratory passage and is termed as dead air space because no exchange of gases takes place here.

Liver is the largest organ in the body. It helps in digestion and removes waste products and worn-out cells from the blood. Liver performs many functions, like it forms and secretes bile that contains bile acids to aid in the intestinal absorption of fats and the fat-soluble vitamins as A, D, E, K and $B _{12}$. Hence, it stores vitamins as A, D, E, K and $B _{12}$.

• The oral and nasal cavities lie near the body midline, inferior and medial to the orbital cavities, anterior to the pharynx and medial to the infratemporal fossa.
• They are separated from one another by the palate. 
• Each cavity has an entrance and an exit. Hence, Nasal chambers and buccal cavity are separated by the palate.

Pharynx  connects the nasal cavity and mouth to the larynx and esophagus. It is the common pathway for food and air. There are three regions nasopharynx, oropharynx, and laryngopharynx. Nasopharynx  an air passage; uvula prevents food from entering it during swallowing. Oropharynx posterior to the mouth, passageway for food and air. Laryngopharynx passageway for food and air. Directly posterior to the epiglottis and extends to the larynx, then becomes continuous with esophagus. 

Small intestine is made up of three parts- duodenum, jejunum and ileum. The intestinal wall bears microscopic finger like projections called villi. The Mucosa layer forms crypts in between the bases of villi in the intestine (crypts of Lieberkuhn). The crypts produce digestive juice.

Various smooth muscle sphincters regulate the flow of bile and pancreatic juice through the ampulla: the sphincter of the pancreatic duct, the sphincter of the bile duct, and the hepatopancreatic sphincter (Sphincter of Oddi).The sphincter of Oddi controls the introduction of bile and pancreatic secretions into the duodenum, as well as preventing the entry of duodenal contents into the ampulla.

Folds of small intestine are conical shaped villi.  Small slit like space is found at the base of villi. These spaces are called crypts of Lieberkuhn. The crypts of Leiberkuhn secrete succus entericus or intestinal juice. The succus entericus mainly contains water (99%) and various digestive enzymes (1%).