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• Digestive system


  Function is digestion, the breakdown of organic compounds into their simple forms for use by the cells
• Digestion


  1. Mechanical breakdown

  2. Chemical breakdown

  3. Food journey from mouth to anus takes 18-20 hours
• Ingestion


  Taking in food or any substance into the body through the mouth
• Digestion


  1. Break down of large food molecules into smaller molecules for easy absorption by cells

  2. Begins in mouth with mechanical and chemical digestion
• Mouth


  • Teeth cut, crush, and break food into tiny pieces
  • Tongue helps mix food with saliva to form bolus
• Mastication


  Mechanical digestion, initial stage of digestion
• Saliva


  Contains salivary amylase enzyme that breaks down starch
• Esophagus


  Transports food and liquids to stomach via peristalsis
• Stomach


  1. shaped, bag-like muscular organ that stores food and turns it into chyme
• Chyme


  Semifluid material formed from bolus acted upon by gastric juices
• Gastric juices


  Hydrochloric acid and pepsin that begin chemical breakdown of proteins
• Liver


  Produces bile that helps digest fats

  biggest organ inside
• Pancreas


  Produces enzymes amylase, peptidase, and lipase that aid in digestion of carbohydrates, proteins, and fats
• Small intestine

  • Breaks down food further into absorbable substances
  • Has three parts: duodenum, jejunum, and ileum
• Absorption


  Passing of soluble food molecules through the villi in the small intestine wall into the bloodstream
• Assimilation


  Movement of digested nutrients into body cells through microvilli
• Large intestine


  • Reabsorbs liquid, electrolytes and some vitamins from undigested food
  • Secretes mucus to aid in feces formation
• Egestion


  Release of undigested food (feces) through the anus
• The cell cycle can be compared to the life cycle of a cell, a series of growth and developmental steps a cell undergoes between its "birth" and reproduction

  
• All living things contain a self-replicating genetic material (DNA) that directs the activities and functions of the cells
• Chromosome


  Packaging of DNA molecules by proteins (histones) into different levels of organization

  
• Parts of a chromosome


  • Chromatids
  • Centromere
  • Short arm (p arm)
  • Long arm (q arm)

  
• Cell cycle


  1. Interphase (cell grows and DNA replicates)

  2. Mitotic phase (chromosomes condense)

  
• Interphase


  Interval between cell divisions where the cell obtains nutrients, metabolizes, grows, and replicates DNA
• Somatic cells


  Body cells with two complete sets of chromosomes (diploid)

  
• Gametes


  Sex cells with one set of chromosomes (haploid)
• Meiosis


  Two cell divisions that reduce the chromosome number from diploid to haploid

  
• Meiosis I


  Reduction division that produces two haploid daughter cells

  
• Prophase I


  • Includes leptotene, zygotene, pachytene, diplotene, and diakinesis substages
• Meiosis I


  1. Prophase I

  2. Metaphase I

  3. Anaphase I

  4. Telophase I

  
• Prophase I


  • Leptotene
  • Zygotene
  • Pachytene
  • Diplotene
  • Diakinesis
• Leptotene


  Each chromosome is made up of sister chromatids

  
• Zygotene


  Homologous chromosomes start to pair off through synapsis

  
• Pachytene


  Repeated coiling of chromosomes, crossing over occurs
• Diplotene


  Two homologous chromosomes forming a tetrad begin to repel one another
• Diakinesis


  Chiasmata terminalization, homologous pair chromosomes distribute evenly in the nucleus

  
• Meiosis is a type of cell division that takes place during the creation of sex cells
• During meiosis, the chromosome number is decreased by half

  
• Gametogenesis


  The creation of germ cells or gametes
• Gametogenesis in males is known as spermatogenesis, in females as oogenesis