Human Nutrition

Digestion in the human body

  1. Begins in the mouth :

    Teeth - Breaks down food into smaller pieces via mastication

    Tongue- accessory organ (is muscular and has papillae where taste buds occur)

    - Helps with chewing by pressing food against hard palate and teeth + mixes food with saliva to roll food into a bolus

    - Helps with swallowing by pushing bolus towards throat

    Salivary glands: Exocrine gland - produces and secretes saliva via ducts that open into oral cavity

    3 glands - Parotid (on top), Sublingual (in the front of mouth), Submandibular ( by throat)

  2. Pharynx - connects mouth to oesophogus and pushes food into oesphogus, with the help of the epiglottis

  3. Oesophogus : Peristalsis occurs here to push bolus towards stomach

  1. Stomach : sac-like

    Muscular walls cause churning movements to assist with mechanical digestion, as well as mixes food with gastric juices

    Gastric glands secrete hydrochloric acid

    Has 2 sphincters: Cardiac sphincter (allows bolus into stomach) and Pyloric sphincter (allows chyme out of stomach)

  2. Pancreas - accessory organ ; tongue shaped gland

    - Is an Endocrine (iselts of Langerhans )(secretes insulin and glucagon) & an Exocrine gland (pancreatic cells secrete digestive juices that gets transported via pancreatic duct, which joins the common bile duct)

  1. Liver - produces bile

    - Glucose gets converted into glucagon for storage in the liver

    - is a detoxifying organ (absorbs and neutralises toxins, such as alcohol)

    - used for deamination (process whereby excess amino acids get broken down into urea and glucose)

    - stores vitamins A, B12, D, E and K

    - synthesis heparin, which controls blood clotting

  1. Gallbladder - stores bile

    - bile is used to emulsify fats

  1. Small intestine - is a long (5 -6m long) muscular tube, has villi to increase the surface area for absorption and is made of 3 parts, namely :

    1. Duodenum

    is the shortest part

    Lieberkuhn & Branner glands secrete digestive juices

    common bile duct (from gallbladder) and pancreatic duct open as a joint tube in duodenum

    1. Jejunum

      is the middle part

    2. Ileum

      last & longest part

      Joins first part of large intestine and is closed by a muscular ring called the ileo-caecel sphincter

  1. Large intestine - first part is called caecum and the second and largest part is the colon

    - secretes large amounts of mucus to aid digestion

    - absorbs water and useful substances (vitamins and bile salts)

    - Rectum then stores undigested waste (faeces) and gets ejected through anus (defecation)