Lab: The Digestive System Part 3 Flashcards
The organs of the digestive tract are lined with a serous membrane consisting of what 3 parts?
- Superficial mesothelium covering a layer of areolar tissue
- Serosa (aka visceral peritoneum)
covers organs within peritoneal cavity - Parietal peritoneum: (lines inner surfaces of body wall)
What kind of tissue composes the mesentaries?
Areolar Tissue
During embryonic development, the digestive tract and accessory organs are suspended in peritoneal cavity by what 2 things?
Dorsal and Ventral Mesentary
What is the function of the lesser omentum?
- Stabilizes position of stomach
2. Provides route for blood vessels and other structures entering or leaving liver
The Dorsal Mesentery enlarges to form an enormous pouch known as what?
The greater omentum
What is the position of the 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
What is the function of the greater omentum?
- conforms to shapes of surrounding organs
- pads surfaces of abdomen
- insulates
- stores lipid energy reserves
What is the mesocolon?
A mesentery associated with a portion of the large intestine
What are Enteroendocrine cells?
Scattered amongst columnar cells. Secrete hormones coordinate activities of the digestive tract.
What are plicae circulares?
Permanent transverse folds in the digestive tract
What are the longitudinal folds in the digestive tract for, and what happens to them?
- Increase surface area for absorption
2. The folds disappear as digestive tract fills
What is the Muscularis mucosae?
Narrow band of smooth muscle and elastic fibers in lamina propria
How are the smooth muscle cells of the Muscularis mucosae arranged?
- inner concentric layer encircles lumen (circular muscle)
2. outer concentric layer contains longitudinal layer
Which layer of the digestive lining has large blood and lymphatic vessels and may contain exocrine glands?
The submucosa
Which layer of the digestive lining Is made of dense, irregular connective tissue?
The submucosa
What innervates the mucosa and submucosa?
The Submucosal Plexus
What is another name for the plexus of Meissner?
The submucosal plexus
Which layer of the digestive lining is Is dominated by smooth muscle cells arranged in and Inner circular layer and Outer longitudinal layer?
The Muscularis (Externa)
What coordinates the movements of the muscularis?
The enteric nervous system (ENS)
What does the Muscularis do?
- Churns food for mechanical prossessing
2. Moves materials along digestive tract
What regions lack Serosa and instead have adventitia?
Oral cavity, Pharynx, Esophagus, and Rectum
What are pacesetter cells?
Cells in the muscularis that control rhythmic cycles of the digestive tract
What triggers a wave of contraction through the muscularis?
Spotaneous deploraization of the muscle cells
Where are pacesetter cells located?
In the muscularis mucosae and muscularis externa
What is Peristalsis?
waves of muscular contractions that move a bolus along the length of the digestive tract
What are the 3 steps of Peristaltic Motion?
- Circular muscles contract behind bolus
- Longitudinal muscles ahead of bolus contract:
Shortening adjacent segments - Wave of contraction in circular muscles pushes bolus forward
What is Segmentation?
Cycles of contraction that churn and fragment the bolus, mixing it with intestinal secretions.
How is segmentation different from peristalisis?
It does not push the bolus in any particular direction.
What 2 things do neural mechanisms control re: digestion?
- movement of materials along digestive tract
2. secretory functions
Where are motor neurons located and what do they do?
- myenteric plexus
2. control smooth muscle contraction and glandular secretion
How many hormones are involved in the digestive process?
At least 18
What produces hormones involved in digestion?
Enteroendocrine cells in digestive tract
What are the 4 functions of the Oral Cavity?
- Sensory analysis
- Mechanical processing
- Lubrication
- Limited digestion (carbs and lipids)
From where and can we rapidly absorb lipid-soluble drugs ?
Thin oral mucosae inferior to the tongue
Whats a fun word for lips?
Labia
Whats a fun word for gums?
Gingivae
What enzyme does the tongue secrete?
Lingual lipase
Which gland is drained by the parotid duct?
Parotid Salivary Glands
Where is the enzyme salivary amylase produced and what does it break down?
Parotid Salivary Glands, starch
What produces mucous secretion that acts as a buffer and lubricant?
Sublingual Salivary Glands
What are on either side of the lingual frenulum?
Sublingual (Rivinal) ducts
What secretes buffers, glycoproteins (mucins), and salivary amylase?
Submandibular Salivary Glands
Where are the submandibular ducts?
immediately posterior to teeth on either side of lingual frenulum
How much saliva is produced per day?
1.0–1.5 liters of saliva each day
What percentage of saliva is produced by each set of glands?
70% by submandibular glands
25% by parotids
5% by sublingual glands
How much of saliva is water?
99.4%
What is Dentin?
A mineralized matrix similar to that of bone
Does not contain cells (Teeth)
What is the Pulp cavity?
Portion of tooth that receives blood vessels and nerves through the root canal
What is the bony socket in which a tooth sits?
alveolus
What providing protection and anchors periodontal ligament?
cementum
What defines the crown of the tooth?
Exposed portion of tooth projecting beyond gingiva
What covers dentin?
Enamel
What is the Alveolar Processes?
a thickened ridge of bone that contains the tooth sockets on the mandible and maxilla
What are the 4 types of teeth?
- Incisors
- Cuspids (canines)
- Bicuspids (premolars)
- Molars
Which teeth are blade shaped and are used for clipping or cutting?
Incisors
Which teeth are conical with a pointed tip
Used for tearing or slashing?
Cupsids / Canines
Which teeth types have 1 root?
Incisors, Canines, some bicupids
Which teeth types have 2 roots?
some bicupids
Which teeth have flattened crowns and are used to crush, mash, and grind?
Bicuspids (premolars)
Which teeth have very large, flat crowns used for crushing and grinding?
Molars
Which teeth have prominent ridges?
Molars, Bicuspids (premolars)
Which teeth types have 3+ roots?
Molars
What are the 2 sets of teeth that develop as embryos?
- deciduous teeth (primary dentition)
2. permanent dentition (secondary dentition)
What are milk teeth, or baby teeth and how many are there?
there are 20 Deciduous Teeth, 5 in each quadrant
,
When may you not have molars?
When you have deciduous teeth as a child
How many permanent teeth does an adult have?
32
How many molars does an adult have?
5 in each quadrant (20 total)
What are the 3 parts of the pharynx?
Nasopharynx
Oropharynx
Laryngopharynx
What prevents air from entering the esophagus?
A circular muscle layer in the superior 3 cm (1.2 in.) of the esophagus
What is deglutition?
Swallowing
What are the 3 phases of deglutition?
- Buccal phase
- Pharyngeal phase
- Esophageal phase
What is intrinsic factor?
A glycoprotein required for absorption of vitamin B12
Between what vertebrae does the stomach extend?
T7 and L3
What are gastric pits?
depressions that denote entrances to gastric glands. deeper in the pylorus
How far do gastric glands reach?
Deep into underlying lamina propria
What do Pyloric Glands produce?
Enteroendocrine cells
G cells produce gastrin
D cells release somatostatin (ant-gastrin)
What regulates the production of acid and enzymes by the gastric mucosa?
- CNS
- short reflexes of ENS
- hormones of digestive tract
Which nerve curves around the top of the stomach?
Vagus Nerve
What occurs during the cephalic phase?
stomach prepares for arrival of food by increasing gastric juices as g cells release gastrin
What occurs during the gastric phase?
- enhances secretion of juices
- prepares chyme (acid + homogenize)
- initiates pepsin digestion of protein
What occurs during the intestinal phase?
controls rate of chyme entry into the duodenum
90% of nutrient absorption occurs
In the small intesine
What 3 things major does the duodenum recieve?
- Chyme
- digestive secretions from pancreas
- bile from liver/gallbladder
Other than absorption, what does the duodenum do?
Neutralize acids before they can damage the small intestine
What has small villi and is the site of the most chemical digestion nutrient absorption?
Jejunum
How long is the Jejunum?
2.5 meters (8.2 ft) long
What is the final segment of the small intestine?
The ileum
How long is the ileum and where does it end?
The 3.5 meters (11.48 ft) long ileum ends at the ileoceval valve
What are Plicae circulares?
Permanent transverse folds in the small intestinal lining
What are Crypts of Lieberkühn?
Openings from small intestinal glands at bases of villi, leading to intestinal lumen
What are Brush Border Enzymes?
Membrane proteins on surfaces of intestinal microvilli that break down materials
What are 2 things produced by intestinal glands?
Enteropeptidase (brush border enzyme activates trypsinogen)
Enteroendocrine cells (Produce intestinal hormones)
What are referred to as submucosal or Brunner glands?
Duodenal Glands
What do Duodenal Glands produce?
copious quantities of mucus (for chyme!)
How many liters of Intestinal Secretions are produced per day?
1.8 liters
What triggers relaxation of ileocecal valve?
The Gastroileal Reflex
What are the 3 regions of the pancreas?
Head Body Tail
What are Pancreatic Acini?
Blind pockets containing scattered pancreatic islets
What are pancreatic islets?
Endocrine tissues of pancreas
What are the 2 major cells of the pancreas”
- Endocrine cells of the pancreatic islets
2. Exocrine cells
What do Endocrine cells of the pancreas do?
Secrete insulin and glucagon into blood stream
What do Exocrine cells of the pancreas do?
secrete pancreatic juice
How much pancreatic juice is secreted per day?
1000 mL (1 qt) pancreatic juice per day
What are 4 pancreatic enzymes?
- Pancreatic alpha-amylase
- Pancreatic lipase
- Nucleases
- Proteolytic enzymes
What is Pancreatic lipase?
Breaks down complex lipids
What is Pancreatic alpha-amylase?
Breaks down starches similar to salivary amylase
What is Nucleases?
Breaks down nucleic acids
What are Proteolytic enzymes?
70% of all pancreatic enzyme production, Break certain proteins apart
What is the largest visceral organ?
The liver
How much does the liver weigh?
1.5 kg; 3.3 lb
How many portal areas does a liver lobule have?
6
What 3 parts make up the portal area of a liver lobule?
- Branch of hepatic portal vein
- Branch of hepatic artery proper
- Small branch of bile duct
Where does the cystic duct lead?
From the liver to the duodenum
Where does the common bile duct lead?
from the gallbladder
What are the 3 jobs of the liver (better 1)
- Metabolic regulation
- Hematological regulation
- Bile production
3 regions of the gallbladder?
- Fundus 2. Body 3. Neck
How much bile is stored in a full gallbladder?
40–70 mL
How long does it take for materials to pass from duodenum to end of ileum?
5 hours
What is the largest portion of the large intestine?
The colon
What is the taeniae coli?
Three longitudinal bands of smooth muscle in the colon that create the haustra
What are fatty appendices?
teardrop-shaped sacs of fat in the serosa of the colon
How long is the sigmoid colon?
15 cm (6 in.) long
Other than vitamin K, what other nutrients are produced by bacteria in the colon?
- biotin 2. Pantothenic acid: B5
When bacteria break down peptides in feces they generate:
- Ammonia
- Indole and skatole (stinky-poop nitrogen compounds)
- Hydrogen sulfide (farts but in the poop)
What is responsible for flatus?
Bacteria feed on indigestible carbohydrates (complex polysaccharides)
What must be digested before absorption can occur?
Large organic molecules
What can be absorbed without processing?
Water, electrolytes, and vitamins
Brush border enzymes break nucleotides into
- Sugars
- Phosphates
- Nitrogenous bases
Effects of aging on the digestive system?
- Division of epithelial stem cells declines:
- Smooth muscle tone and general motility decreases
- Cumulative damage from toxins
- Risk of Colon cancer and stomach cancer increase
- Decline in olfactory and gustatory sensitivity
