Nutrition in Humans - O-Level Biology

Vocabulary flashcards covering the human digestive system, the stages of nutrition, and the roles of associated organs and enzymes based on the O-Level Biology syllabus.

Nutrition

The process by which organisms obtain food and energy for growth, repair and maintenance of the body.

Ingestion

The intake of food into the body.

Digestion

The process where large food molecules are broken down into small and soluble forms.

Absorption

The process by which digested food materials are taken into the body.

Assimilation

The process where absorbed food materials are used by the cells.

Egestion

The removal of undigested food materials from the body.

Teeth

Structures that physically break large pieces of food into smaller pieces to increase surface area to volume ratio for enzymes to act more efficiently.

Salivary glands

Glands that secrete saliva containing salivary amylase to break down starch to maltose.

Tongue

An organ that mixes food with saliva and rolls it into a bolus, pushing it down the oesophagus during swallowing.

Epiglottis

A structure that covers the entrance of the trachea (windpipe) during swallowing to prevent choking.

Oesophagus

A narrow, muscular tube that transports food from the pharynx to the stomach through peristalsis.

Peristalsis

Rhythmic wave-like contractions of the circular and longitudinal muscles to mix and propel the contents of the alimentary canal.

Antagonistic muscles

Pairs of muscles like the circular and longitudinal muscles in the oesophagus; when circular muscles contract, longitudinal muscles relax, and vice versa.

Stomach

A distensible muscular bag that stores food temporarily and physically breaks it down for chemical digestion.

Chyme

The liquified form of partially digested food that is formed in the stomach.

Gastric juice

A secretion from gastric glands containing hydrochloric acid at $pH\,2$ and enzymes like pepsin.

Hydrochloric acid

A component of gastric juice that denatures salivary amylase, kills harmful bacteria, and provides the optimal pH for protease.

Pepsin

A protease enzyme in the stomach that digests proteins into polypeptides.

Pyloric sphincter

A muscular ring at the end of the stomach that controls how much chyme is passed into the small intestine.

Small intestine

A muscular tube about $5-6\,m$ long, consisting of the duodenum, jejunum, and ileum, where chemical digestion and absorption occur.

Villi

Numerous finger-like projections in the small intestine that increase surface area for the faster absorption of glucose, amino acids, and fats.

Lacteal

Also known as lymphatic capillaries, these are located in the villi and are responsible for the absorption of fats.

Colon

Part of the large intestine responsible for absorbing remaining water and mineral salts from undigested food substances.

Rectum

Part of the large intestine that stores undigested food substances before egestion.

Anus

The opening at the end of the alimentary canal through which faeces (undigested matter) is egested.

Liver

An organ whose cells produce and secrete bile to physically digest (emulsify) fat molecules.

Gall bladder

A greenish-yellow bag that stores bile temporarily and releases it into the small intestine through the bile duct.

Pancreas

An organ that produces pancreatic juice containing amylase, protease, and lipase, as well as hormones like insulin and glucagon.

Hepatic portal vein

A blood vessel that transports blood rich in absorbed nutrients (glucose and amino acids) from the small intestine to the liver.

Hepatic artery

A blood vessel that transports oxygenated blood from the heart to the liver.

Hepatic vein

A blood vessel that transports deoxygenated blood away from the liver towards the heart.