Digestive System Flashcards
Alimentary canal
-mouth
-pharynx
-esophagus
-stomach
-small intestine
-large intestine
Differentiate between organs of alimentary canal and accessory organs or structure.
-The alimentary canal, or GI tract, is the continuous muscular digestive tube that winds through the body digesting and absorbing foodstuff; its organs include: the mouth, pharynx, esophagus, stomach, small intestine, and large intestine.
-Accessory digestive organs or structures aid digestion physically and produce secretions that break down foodstuff in the GI tract; the organs involved are the teeth, tongue, gallbladder, salivary glands, liver and pancreas.
6 functions of digestive system
- Ingestion:
■ occurs when materials enter digestive tract - Propulsion:
■ Peristalsis (movement of food through tract) - Mechanical breakdown:
■ Teeth
■ Tongue
■ Stomach churning
■ Segmentation - Digestion:
■ is the chemical breakdown of food
■ into small organic fragments
■ for absorption by digestive epithelium - Absorption:
■ movement of nutrients
■ across digestive epithelium
■ into interstitial fluid of digestive tract - Defecation :
■ Eliminate indigestible substances in feces
Lining of digestive tract
■ Protects surrounding tissues against:
■ corrosive effects of digestive acids and enzymes
■ mechanical stresses, such as abrasion
■ bacteria
Name one organ of the alimentary canal found in the thorax. Name 3 organs located in abdominal cavity.
Esophagus;
Stomach, small intestine, large intestine
Which digestive system activity actually moves nutrients from outside to inside the body?
Absorption
Bacteria
■ Is ingested with food or resides in digestive tract
■ Attacked by macrophages, and immune system cells
■ In lamina propria (underlying layer of areolar tissue)
Peritoneal cavity
■ Is located within the abdominopelvic cavity
■ Lined with peritoneum (simple squamous epithelium) membrane consisting of:
■ superficial mesothelium covering a layer of areolar tissue
Parietal and visceral layers
-of peritoneum
-continuous w/ one another via several extension (mesenteries, falciform ligament, lesser and greater omenta)
-separated by a potential space containing serous fluid, which decreases friction during organ activity
All organs of GI tract have the same basic pattern of tissue layers in their walls
All have mucosa, submucosa, muscular externa, and serosa (or adventitia). Intrinsic nerve plexuses (enteric nervous system) are found w/in the wall
Digestive viscera are served by the…
Splanchnic circulation, consisting of aterial branches of the celiac trunk and aorta and hepatic portal circulation
How does the location of the visceral peritoneum differ from that of the parietal peritoneum?
Visceral- outermost layer of digestive organ
Parietal- serous membrane covering the wall of abdominal cavity
Peritoneal fluid
■ Is produced by serous membrane lining
■ Provides essential lubricant
■ Separates parietal and visceral surfaces
■ Allows sliding without friction or irritation
Peritoneal cavity disorders
■ Peritonitis
■ Inflammation of the peritoneal membrane
■ Caused by:
■ piercing abdominal wound
■ perforating ulcer
■ ruptured appendix
■ Membranes stick together, localizing infection
■ Can be fatal w/bacterial invasion
■ Ascites
■ The accumulation of Peritoneal Fluid that causes abdominal effusion
■ Can distort abdominal organs and result in:
■ heartburn,
■ indigestion
■ lower back pain.
Peritoneal cavity disorders
■ Peritonitis
■ Inflammation of the peritoneal membrane
■ Caused by:
■ piercing abdominal wound
■ perforating ulcer
■ ruptured appendix
■ Membranes stick together, localizing infection
■ Can be fatal w/bacterial invasion
■ Ascites
■ The accumulation of Peritoneal Fluid that causes abdominal effusion
■ Can distort abdominal organs and result in:
■ heartburn,
■ indigestion
■ lower back pain.
Of the following, which is/are retroperitoneal?
Stomach, pancreas, liver
Pancreas
What is the name of the venous portion of splanchnic circulation?
Hepatic portal circulation
Mesenteries
■ Are double sheets of peritoneal membrane
■ Suspend portions of digestive tract within peritoneal cavity by sheets of serous membrane:
-that connect parietal peritoneum
-with visceral peritoneum
■ Areolar tissue between mesothelial surfaces:
-provides an route to and from the digestive tract
-for passage of blood vessels, nerves, and lymphatic vessels
■ May attain status as a separate organ
-One contiguous structure
-Functions not well understood
■ Stabilize positions of attached organs
■ Prevent intestines from becoming entangled
Describe the location and function of peritoneum.
The peritoneum is a serous membrane that covers the abdominal walls and most abdominal organs. It has two layers, the inner (visceral) layer and the outer (parietal) layer. It provides protection and stability to the abdominal organs, allowing minimal movement.
Retroperitoneal
Give examples
Retroperitoneal: regarding anything that is posterior to the mesentery, lying against dorsal abdominal wall.
-Organs: most of the duodenum, the pancreas, ascending and descending colon, and the rectum.
Splanchnic circulation and indicate the important of hepatic portal system.
blood flow through the abdominal organs including the stomach, liver, pancreas, spleen, and intestines, while the hepatic portal system is a specific part of this circulation that delivers nutrient-rich blood from the digestive tract directly to the liver via the hepatic portal vein, allowing the liver to process absorbed nutrients and toxins before they enter the systemic circulation
the hepatic portal system is crucial for the liver’s vital functions in regulating blood chemistry and metabolism
Tissue composition and general function of 4 layers of alimentary canal
- Mucosa - innermost layer - SECRETION of mucous, digestive enzymes, and hormones. ABSORPTION of end products of digestion into the blood. PROTECTION against infection.
- Submucosa - extensive VASCULAR network supplies surrounding tissue, ELASTIC fibers enables stomach to regain normal shape after large meal.
- Muscularis Externa - SEGMENTATION and PERISTALSIS. Forms sphincters that act as valves.
- Serosa - Outermost layer - PROTECTIVE layer of areolar connective tissue covered with mesothelium.
Mesenteries development
■ During embryonic development:
-digestive tract and accessory organs are suspended in peritoneal cavity by:
-dorsal mesentery
-ventral mesentery
When sensors in the GI tract are stimulated they trigger reflexes. What types of digestive activity may be put into motion via those relfexes?
Reflexes associated with/ the GI tract promote muscle contraction and secretion of digestive juices or hormones
The term “gut brain” does not really mean there is a brain in the digestive system. What does it refer to?
Enteric nervous system, the web of neurons closely associated w/ the digestive organs
Jerry has been given a drug that inhibits parasympathetic stimulation of his digestive tract. Should he “eat hearty” or temporarily refrain from eating? Why?
Temporarily refrain from eating b/c parasympathetic NS stimulated digestive activities
Lesser omentum
-stabilizes position of stomach
-provides access route for blood vessels and other structures entering or leaving liver
Dorsal mesentery
■ Is on ventral surface of stomach
■ Enlarges to form an enormous pouch, called the greater omentum
Greater omentum
■ Extends inferiorly between:
-the body wall and
-the anterior surface of small intestine
■ Hangs like an apron:
-from lateral and inferior borders of stomach and attaches to the large intestine
■ Adipose tissue in greater omentum:
-pads and protects surfaces of abdomen
-provides insulation to reduce heat loss
-stores lipid energy reserves
-Contains many lymph nodes- site of peritoneal immune response
Describe stimuli and controls of digestive activity
Digestive activities within the GI tract are triggered by mechanical and chemical stimuli [e.g., stretching of organ by food, osmolarity, pH, etc.] and are detected by mechanoreceptors and chemoreceptors.
• Controls of digestive activity are both intrinsic [“in-house”] and extrinsic.
a. Neural mechanisms [Enteric Nervous System (ENS)]: the ENS has roughly as many neurons as the spinal cord, and as many neurotransmitters as the brain, but whose functions remain largely unknown…
❊ Short [myenteric] reflexes control smooth muscle contraction and glandular secretion as relatively localized activities involving small segments of the digestive tract; this mechanism is usually considered parasympathetic, but the plexus also contains sensory neurons, motor neurons and interneurons for local reflexes whose internal workings operate entirely outside the control of the CNS.
❊ Long reflexes involve interneurons and motor neurons in the CNS and provide a higher level of control over digestive and glandular activities.
b. Hormonal mechanisms involve as many as 18 hormones, affecting almost every aspect of digestive function.
c. Local mechanisms involve prostaglandins, histamines and other chemicals released into the interstitial fluid and affecting adjacent cells…
Oral mucosa tissue type
Stratified squamous epithelial
Tongue
-mucosa-covered skeletal muscle
-intrinsic muscles: allow change of shape
-extrinsic muscles: allow change in position
Saliva
-produced by minor salivary glands and 3 pairs of major salivary glands: parotid, submandibular, and sublingual
-largely water, contains ions, proteins, metabolic wastes, lysozyme, defensins, IgA, salivary amylase, and mucin
-moistens and cleanses the mouth
-moistens food, aiding their compaction
-dissolves food chemical to allow for taste
-begins digestion of starch (salivary amylase)
-saliva output ⬆️ by PNS initiated by activation of chemical and pressure receptors in the mouth and by fight or smell of food
Teeth
-bulk of tooth is dentin, which surround the central pulp cavity
-periodontal ligament secures the tooth to bony alveolus
Mesentery proper
■ Is a thick mesenterial sheet
■ Permits some independent movement
■ Suspends all but first 25 cm of small intestine
■ Does not surround the initial portion of small intestine (duodenum) and pancreas (they are retroperitoneal)
■ Fuses with posterior abdominal wall, locking structures in position
Which structure forms the roof of the mouth?
Palate forms roof of mouth. Hard palate supported by bone is anterior to soft palate (no bony support)
Name 3 antimicrobial substances found in saliva.
-lysozyme
-defensins
-IgA antibodies
Which tooth substance is harder than bone? Which tooth regions includes nervous tissue and blood vessels?
Enamel is harder than bone
Pulp consists of nervous tissue and blood vessels
Describe the composition and functions of saliva, and explain how salivation is regulated
Salivary glands produce saliva, which cleanses the mouth, dissolves food chemicals for taste, moistens food, and contains chemicals that begin the breakdown of starches.
Saliva Composition: 1.0-1.5 liters/day, 97- 99.5% water, but also IgA, lysozyme, defensins, mucins and salivary amylase; production of a bolus.
Regulation: Parasympathetic [watery saliva] and sympathetic [more viscous saliva] stimulation.
Mesocolon
■ A mesentery associated with a portion of the large intestine:
-transverse mesocolon supports transverse colon
-sigmoid mesocolon supports sigmoid colon
-Ascending and descending colon are retro peritoneal
Blood supply: Splanchnic circulation
■ Branches of aorta serving digestive organs
-Hepatic, splenic, and left gastric arteries
-Inferior and superior mesenteric arteries
■ Hepatic portal circulation
-Drains nutrient-rich blood from digestive organs
-Delivers it to the liver for processing
Digestive epithelium
■ Mucosal epithelium is simple or stratified:
-depending on location, function, and stresses
■ Oral cavity, pharynx, and esophagus:
■ mechanical stresses
■ Stomach, small intestine, and most of large intestine:
-absorption
-simple columnar epithelium with goblet cells
Enteroendocrine cells
■ Are scattered among columnar cells of digestive epithelium
-Secrete hormones that:
-coordinate activities of the digestive tract and accessory gland
Lining of digestive tract
■ Folding increases surface area for absorption:
– longitudinal folds, disappear as digestive tract distends
– permanent transverse folds (plicae)
Deglutition (swallowing)
Buffalo phase
-upper esophageal sphincter is contracted (closed)
-tongue presses against hard palate, forcing food boils into oropharynx
Deglutition: pharyngeal-esophageal phase begins
-tongue blocks mouth
-soft palate and its uvula rise, closing off nasopharynx
-larynx rises so that epiglottis blacks trachea
-upper esophageal sphincter relaxes; food enter esophagus
Deglutition: pharyngeal esophageal phase continues (steps 3-5)
3)
-constrictor muscles of pharynx contract, forcing food into esophagus inferiorly
-upper esophageal sphincter contracts after food enter
4)
-peristalsis moves food through esophagus to stomach
5)
-gastro esophageal sphincter orifice opens. After food enter the stomach sphincter closes, preventing regurgitation
Esophagus extends…
Extends from laryngopharynx and joins the stomach at cardial orifice, which is surrounded by gastroesophageal sphincter
