1. Human Digestive System

9. Swallowing

10. What Happens During Breathing and Swallowing? trachea (windpipe) glottis During breathing, the larynx is lowered and the glottis is open. pharynx oesophagus larynx (voice-box) air Normally, air passes into the trachea ( windpipe ) while food passes into the oesophagus .

11. What Happens During Breathing and Swallowing? During swallowing, the larynx is raised and the glottis is covered by the epiglottis . This prevents food particles from entering the trachea. pharynx trachea (windpipe) oesophagus glottis epiglottis food particles larynx (voice-box)

12. What Happens During Breathing and Swallowing? Occasionally, small particles of food or water may get into the larynx or trachea. trachea (windpipe) larynx (voice-box) food particles

13. What Happens During Breathing and Swallowing? This automatically induces violent coughing to force the food particles or water out and to prevent choking. trachea (windpipe) larynx (voice-box) food particles

16. Wall here constricts. Circular muslces contract; longitudinal muscles relax Wall here dilates Direction of movement of food Circular muscles relax Longitudinal muscles contract

19. HCl converts inactive pepsinogen and prorennin to their active forms

33. Lacteal – fatty acids and glycerol recombine in the epithelium to form fat which then enters the lacteal as fine fat droplets Blood capillaries – transport sugars and amino acids away from the small intestine One cell thick epithelium – for efficient absorption of food particles This continual transport of digested food substances maintains the concentration gradient for the absorption of digested food substances.

35. What happens to amino acids and glucose after absorption? Products released from liver into general blood circulation Molecules pass into the epithelial cells Through walls of capillaries in the villus and into bloodstream The capillaries join up to form veins Veins unite to form 1 large vein: Hepatic Portal Vein Hepatic portal vein carries blood to liver Liver stores or alters products of digestion

38. What happens to fatty acids and glycerol after absorption? Molecules pass into the epithelial cells Recombine into fats again in the epithelial cells Fats enter the lacteals Lymph (fluid in lacteals) + fat = chyle Lymphatic vessels discharge chyle into bloodstream

40. Villi – absorption by diffusion Diffusion From intestine To To liver