science

• Digestive system


  Complex network of organs that work together to break down food into nutrients that the body can absorb and use for energy, growth, and repair
• Organs of the digestive system

  • Mouth
  • Esophagus
  • Stomach
  • Small intestine
  • Large intestine
  • Liver
  • Gallbladder
  • Pancreas
• Chromosome


  The fundamental genetic material that carries the instructions for the organism's development, growth, and functioning
• Centromere


  • A specialized region of the chromosome that helps in its division during cell replication
• Mouth


  • Mechanical digestion: Teeth and tongue break food down into smaller pieces
  • Chemical digestion: Salivary glands produce saliva, Chemicals (Enzymes) in saliva begin to break down food, Amylase breaks down starch into glucose
• Chromatid


  Duplicate copies of a chromosome produced during DNA replication, connected at the centromere
• Cell Membrane


  Where the chromosomes reside. The nuclear membrane serves to separate the chromosomes from the cell's cytoplasm and other contents
• Nucleus


  Where the chromosomes are tightly coiled around proteins. Humans have 23 pairs of chromosomes altogether, and they can only be easily observed during cell division
• Your body produces 1.5L of saliva each day
• All living things contain the genetic material that serves as the set of instructions that direct the activities and functions of the cells. These genetic materials, also known as the deoxyribonucleic acid or DNA, are passed on from one generation to the next to ensure the continuity of life
• Nucleosome


  The basic structural unit of DNA packaging in eukaryotic cells. It consists of DNA wrapped around a core of histone proteins
• Supercoiling


  The coiling of DNA strands upon themselves, resulting in additional twists beyond the typical double helix structure. There are two types: positive and negative
• Primary structure


  The basic structure of DNA is a double helix, where two strands of DNA wind around each other in a spiral. This is the first level of coiling
• Secondary structure


  DNA can coil around histone proteins to form nucleosomes, which are the basic units of chromatin. This wrapping of DNA around histones helps to further compact the DNA molecule
• Tertiary structure


  Chromatin fibers can further coil and fold into higher-order structures, which eventually condense into chromosomes during cell division
• Peristalsis


  Involuntary rhythmic contractions (wave-like) that move food through the digestive system

  
• Histones


  A family of proteins that play a key role in the packaging of DNA into chromatin. They form octameric complexes called nucleosomes, around which DNA is wrapped
• DNA double helix


  The three-dimensional structure formed by two complementary strands of DNA that wind around each other in a spiral shape
• Prophase


  The first and longest phase of mitosis. Chromatin condenses into double stranded sister chromatids, and the nuclear envelope breaks down

  
• Metaphase


  Spindle fibers attach to the centromere of each pair of sister chromatids. The sister chromatids line up at the equator, or center, of the cell
• Anaphase


  Sister chromatids separate and the centromeres divide. The sister chromatids are pulled apart by the shortening of the spindle fibers
• Telophase


  The chromosomes begin to uncoil and form chromatin. The spindle also breaks down, and new nuclear membranes form, dividing the cytoplasm to form two daughter cells

  
• Cell Cycle


  The chromosomes of a cell change form as the cell transitions from one stage to another. It has two stages: interphase and cell division phase

  
• DNA synthesis

  The process by which a cell makes an identical copy of its DNA, occurring during the S phase of interphase
• Esophagus


  • Approximately 20 cm long
  • Secretes mucus and moves food from the mouth to the stomach using peristalsis

  
• Stomach


  • J-shaped muscular bag that stores food and breaks it down into tiny pieces
  • Mixes food with gastric juices that contain enzymes to break down proteins and liquids
  • Hydrochloric acid kills bacteria
  • Food in the stomach is called chyme
  • Functions: food storage, formation of chyme, initiation of protein digestion
• Small intestine digestion


  • Carbohydrates have barely started digestion
  • Protein segments from stomach
  • Fats are not yet digested
• Small intestine


  • Nutrients from food pass into the bloodstream through the walls
  • Absorbs: 80% ingested water, vitamins, minerals, carbohydrates, proteins, lipids
  • Secretes digestive enzymes
  • Roughly 7 meters long
  • Lining has finger-like projections called villi to increase surface area, which are covered in microvilli to further increase surface area for absorption
• Large intestine


  • About 1.5 meters long
  • Absorbs nutrients left behind by the small intestines
  • The end is the rectum, which holds feces before it is expelled
  • Digestion does not take place, it concentrates and eliminates waste material
  • Absorbs water and salt
  • Billions of helpful bacteria break down undigested material
• Functions of the large intestine


  • Bacterial digestion and fermentation of carbohydrates
  • Absorbs additional water
  • Concentrates wastes
• Rectum


  • Temporary storage of feces
• Anus


  • Exit of feces
• Accessory organs


  • Gallbladder
  • Pancreas ● liver
• Gallbladder


  • Stores bile from the liver and releases it into the small intestine
  • Fatty diets can cause the formation of gallstones
• Pancreas


  • Produces digestive enzymes to digest fats, carbohydrates and proteins
  • Regulates blood sugar by producing insulin
  • Produces bile that aids in the digestion of fat
  • Filters out toxins and waste including drugs, alcohol and poisons
• Steps of the digestive system

  1. Ingestion: Food is taken into the body

  2. Digestion: Carbohydrates, proteins and fats are broken down into solute glucose, amino acids, fatty acids and glycerol

  3. Absorption: Glucose, amino acids, fatty acids and glycerol are absorbed into body cells

  4. Assimilation: Absorbed nutrients are transported and utilized by the body

  5. Egestion: Removal of undigested food