Flashcards in Digestive System Deck (72)
What is meant by digestion?
Chemical breakdown of ingested food into absorbable molecules.
What is meant by absorption?
Movement of nutrients, water and electrolytes through the epithelial lining of the gut into blood or lymph.
Describe the enamel of the tooth.
- crystalline rods or prisms of calcium
phosphate & carbonate
- no cells
- hardest tissue of the body
- no sensation
Describe the dentine of the tooth.
Similar to bone but cells (odontoblasts)
occur nearby in the pulp instead of scattered
through the dentine
Describe the pulp of the tooth.
- soft tissue
- blood vessels, nerves, lymphatics
What is the cementum of the tooth?
calcified connective tissue covering the root
Describe the periodontal ligament of the tooth?
- collagen fibres linking the bone of the
socket (alveolar bone) to the cementum
- rapid turnover
What happens in periodontal disease?
The periodontal ligament becomes loose when bacteria infect them
What are the two types of papilli? Which contains taste buds?
Fungiform (taste buds) and filiform
What are the four main tastes?
Sweet, sour, salty, bitter
WHat are the three types of muscles found in the tongue?
Transverse, vertical, longitudinal
What are the gustatory pores?
Pores between taste buds
Do taste buds have nerves?
What is meant by circumvallate?
Being any of the 12 big papillae with many taste buds found near the back of the tongue
What are the three pairs of salivary glands? What do they each secrete?
Parotid: serous fluid (watery)
Submandibular: (mixture of serous fluid and mucous)
Sublingual: mucous (mucous
What do the major salivary glands secrete in response to?
Parasympathetic stimulation induced by seeing, smelling,
tasting or thinking about food.
What is saliva made up of?
Water, mucous and enzymes
Enzymes include: amylase (breaks down starchy debris around teeth) and lysozyme (antibacterial)
What is the general arrangement of abdominal gastrointestinal organs?
- Parietal peritoneum
- Visceral peritoneum
- Peritoneal cavity
Intraperitoneal organs: within the peritoneal cavity
Retroperitoneal organs: behind the peritoneum
What is the greater omentum?
A large fold of the visceral peritoneum that hangs down from the stomach
What is the mesocolon?
A broad, mesofold of peritoneum, which connects the transverse colon to the posterior wall of the abdomen.
How does the peritoneum assist the digestive system?
It needs a good blood and lymph supply. Peritoneum supplies this. It also holds the organs to limit their movement while the person is moving.
Describe the steps of gaining surface area in the gut tube.
Simple tubular glands (Food goes into glands and pits)
Finger-like projections (villi)
Throughout the length of the gut tube we can recognise _____ tunics making up the wall.
What do the other regions of the tube apart from the small intestine differ principally in?
Specialised features of the mucous membrane. The outer three tunics are less variable.
What is the first layer of the gut wall? Describe what it consists of.
Mucosa (mucous membrane) consisting of:
• epithelium, (specialised for protection or absorption or secretion or combinations of all three).
• lamina propria, (a soft fibrous bed of loose connective tissue on which the epthelium rests; carries nerves and blood capillaries, populated with defensive cells).
• muscularis mucosae, (two thin layers of smooth muscle, inner circular and outer longitudinal). This provides the mucosa with some movement independent of the external
muscle coat (e.g. contractions squeeze secretions from glands or lymph along lacteals).
What is the second layer of the gut wall?
Submucosa, a thick bed of loose connective tissue carrying larger blood vessels, lymphatic vessels and nerves (submucosal plexus). It connects the mucosa to the external muscle coat, but allows some movement between the two. For removing products of digestion.
What is the third layer of the gut wall?
Muscularis externa (external smooth muscle), in two layers to produce peristalsis. The inner layer is circular, the outer is longitudinal. The myenteric nerve plexus occurs between the layers.
What is the lowest level of the gut wall?
Serosa, a slippery outer covering for the gut tube (except oesophagus). It is two layered, with outer mesothelium sitting on a bed of connective tissue. The serosa is also known as the visceral peritoneum. Where a structure is not in contact with the body cavity, the outermost connective tissue layer is referred to as the adventitia.
What is secreted in the mouth, small intestine and large intestine?
Mouth: water, saliva, enzymes
Small intestine: bile and enzymes
Large intestine: mucous