Digestive System

• Digestive system


  Responsible for ingestion of food, digestion of food, absorption of nutrients, and elimination of wastes
• Functions of the digestive system

  • Ingestion of food
  • Digestion of food
  • Absorption of nutrients
  • Elimination of wastes
• Anatomy and histology of the digestive tract

  • Mucosa (innermost layer, resists abrasion, absorption and secretion)
  • Submucosa (nerves, blood vessels, small glands)
  • Muscularis (inner circular, outer longitudinal layers, with nerve plexus between)
  • Serosa/adventitia (peritoneum or connective tissue layer)
• Layers of the digestive tract

  • Mucosa
  • Submucosa
  • Muscularis
  • Serosa/adventitia
• Enteric nervous system


  Nerve plexuses between the layers of the digestive tract
• The digestive system starts with the oral cavity
• Oral cavity


  • Lips (orbicularis oris muscle)
  • Cheeks (buccinator muscle)
  • Tongue (taste buds, frenulum)
• Functions of the oral cavity

  • Mastication (chewing)
  • Mechanical digestion
• Five broad categories of taste

  • Sweet (glucose)
  • Salt (sodium chloride ions)
  • Sour (hydrogen ions)
  • Bitter (alkaloids and toxins)
  • Umami (amino acids like glutamate and aspartate)
  • Hot and spicy (pain receptors)
• Tongue contains taste buds and lymphatic tissues
• Teeth


  • Central incisor
  • Lateral incisor
  • Canine
  • First premolar
  • Second premolar
  • First molar
  • Second molar
  • Third molar (wisdom tooth)
• Milk teeth


  • Central incisor
  • Lateral incisor
  • Canine
  • First molar
  • Second molar
• Pulp cavity


  Center of the tooth containing blood vessels, nerves, and connective tissues
• Dentin


  Surrounds the pulp cavity, a living, cellular, bonelike structure
• Enamel


  Covers the dentin, extremely hard, acellular substance that protects the tooth
• Cementum


  Covers the surface of the dentin in the root, helps anchor the tooth in the jaw
• Alveoli/alveolar bone


  Where the teeth are rooted in the maxilla or mandible
• Periodontal ligaments


  Extend from the alveolar walls and are rooted within the cementum
• Gingiva/gums


  Dense fibrous connective tissue and moist stratified squamous epithelium covering the alveolar processes
• Parts of the palate

  • Hard palate (anterior part)
  • Soft palate (posterior part, with uvula)
• Major salivary glands


  • Parotid (largest)
  • Submandibular
  • Sublingual
• Saliva


  Mixture of serous and mucous fluids, 1,000 mL secreted per day, contains amylase, lysozyme, and pH neutralizers
• Parts of the pharynx

  • Nasopharynx
  • Oropharynx
  • Laryngopharynx
• The pharynx connects the mouth with the esophagus
• Hormones are chemical messengers produced by specific cells or organs, which travel through the blood to target tissues where they bind with receptors on cell surfaces.
• The endocrine system is made up of glands that secrete hormones into the bloodstream.
• Endocrine system is made up of endocrine glands that produce hormones and release them into the bloodstream.
• Pituitary gland is located at the base of the brain and produces several important hormones such as growth hormone, thyroid-stimulating hormone, adrenocorticotropic hormone, follicle-stimulating hormone, luteinizing hormone, prolactin, oxytocin, antidiuretic hormone, melatonin, and proopiomelanocortin.
• Pituitary gland - located at base of brain, produces growth hormone, prolactin, follicle-stimulating hormone (FSH), luteinizing hormone (LH), thyrotropin (TSH), melanocyte-stimulating hormone (MSH), antidiuretic hormone (ADH)
• Thyroid gland - located in front of neck, produces calcitonin, thyroxine (T4), triiodothyronine (T3)
• Thymus gland plays a role in immune function.
• Pancreas produces insulin and glucagon, which regulate blood sugar levels.
• Examples of endocrine glands include the pituitary gland, thyroid gland, adrenal glands, ovaries (in females), testes (in males), and pineal gland.
• Thyroid gland is located in the neck and produces thyroid hormones (T3 and T4) and calcitonin.
• Parathyroid glands are four small glands located behind the thyroid gland and produce parathyroid hormone (PTH).
• Adrenal glands consist of two parts - the outer part called the cortex and the inner part called the medulla. The cortex produces steroid hormones such as aldosterone, cortisol, and sex hormones like testosterone and estrogen. The medulla secretes epinephrine and norepinephrine.
• Pancreas - organ involved in digestion and glucose regulation, also secretes insulin and glucagon
• Adrenal glands are paired organs located on top of kidneys and consist of two parts: cortex and medulla.
• Testes produce testosterone in males.
• Ovaries produce estrogen and progesterone in females.