Digestive system Flashcards

1
Q

Abdominal regions

A

Ab regions
- Most digestive organs are in the abdominopelvic cavity
9 regions
- 3 superior: right and left hypochondriac, central epigastric
- 3 middle- right and left lumbar regions, central umbilical region
- 3 inferior- right and left iliac regions, central hypogastric

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2
Q

Peristalsis and segmentation

A

Peristalsis
- Wave of muscular contraction occurs throughout the GI tract
- Adjacent segments alternatively contract and relax
Segmentation
- Back and forth churning that occurs mainly in the small intestine
- Non- adjacent segments alternatively contract and relax

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3
Q

Digestive system processes/ functions

A

Ingestion: acquisition of nutrients
Propulsion: Movement of food through the GI tract (peristalsis)
Mechanical breakdown: Chewing, churning and segmentation
Digestion: Food molecules are broken down
Absorption: Transport of nutrients from the digestive system to the circulatory system
Defacation: Elimination of feces

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4
Q

The peritoneal cavity and peritoneum

A

Visceral peritoneum: covers the external surfaces of most digestive organs
The parietal peritoneum: lines the body wall and is continuous with the visceral peritoneum
Peritoneal cavity: between the visceral and parietal peritoneum, contains fluid to reduce friction

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5
Q

Mesenteries

A

A double layer of peritoneum that extends from the body wall to the digestive organs.
Functions= Hold organs in place, store fat, route for vessels
Ventral mesenteries
- Falciform ligament: liver to anterior abdomen wall and diaphragm
- Lesser omentum: liver to the lesser curvature of the stomach
- Greater omentum: greater curvature of stomach to posterior abdominal wall
Dorsal mesenteries
Greater momentum: Greater curvature of stomach to posterior abdominal wall
Mesentary= supports coils of jejunum and ilium
Transverse mesocolon:
- Transverse colon to posterior abdominal wall
Sigmoid mesocolon= sigmoid colon to posterior pelvis wall

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6
Q

Intraperitoneal vs Retroperitoneal

A
  • Organs that are suspended into the peritoneal cavity contain mesenteries, are referred to as intraperitoneal organs, and are moveable
  • Organs that are not suspended into the peritoneal cavity lack mesenteries, are retroperitoneal and are immobile. e.g. pancreas, kidneys, duodenum, ascending and descending colon
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7
Q

Anatomy of the alimentary canal wall

A

Same 4 layers from the oesophagus to the anus
- The mucosa- innermost layer
Consists of epithelium, lamina propria, muscularis mucosae
- The submucosa- external to the mucosa, contains blood and lymphatic vessels, nerve fibers
- The muscularis externa- external to the submucosa
2 layers: Circular muscularis- inner layer and longitudinal muscularis- outer layer
- The serosa: the outermost layer

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8
Q

Oral cavity

A
  • Entranceway for food
  • Oral vestibule- space between teeth and lips
  • oral cavity proper
  • Hard and soft palate- form roof of mouth
  • Palatoglossal arch- anchors tongue to soft palate
  • Palatopharyngeal arch- anchors tongue to oropharynx
  • Lined with thick stratified epithelium
    Oropharyngeal isthmus is the entranceway from the oral cavity to the pharynx
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9
Q

The tongue

A

Functions
- Assistance in chewing
- Sensory fxn: touch, temperature and taste
- Secretion of mucins and the enzyme lingual lipase that aids in breaking down triglycerides
3 types of projections of mucosa:
- Filiform- roughen
- Fungiform and vallate
- Papillae- tastebuds

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10
Q

Tonsils

A

Patches of lymphatic tissue are found at the entrance of the pharynx. Projection against ingested and inhaled pathogens
- Pharyngeal tonsils are in the posterior wall of the nasopharynx
- Palatine tonsils are in the posterolateral region of the oral cavity
- Lingual tonsils are along the posterior 1/3 of the tongue

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11
Q

Salivary glands

A

Functions= lubricate the oral cavity and moisten food. Dissolve chemicals that stimulate the taste buds. Anti-microbial substances. Parasympathetic innervation stimulates salivary gland secretion
Parotid
- Anterior to the ear
- 25-30% of saliva passes to oral
- Cavity via the parotid duct
- Glossopharyngeal nerve
Sublingual
- Inferiorly to the tongue
- 3-5% of saliva passes to oral cavity via sublingual ducts
- Facial nerve
Submandibular
- Inferior to the mandible
- 60-70% of saliva passes to mouth floor via submandibular duct
- Facial nerve

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12
Q

Mastication

A

Jaw opening muscles:
- Digastric: TMJ depression and larynx elevation
- Mylohyoid: TMJ depression, floor of mouth elevation and hyoid elevation
- Geniohyoid: TMJ depression, larynx elevation and hyoid retraction
Jaw closing muscles:
- Masseter: TMJ elevation, retraction and protraction of the mandible, side-to-side movements
- Medial pterygoid =: TMJ elevation, side-to-side movements

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13
Q

Esophagus

A

From the mouth, food passes into the oropharynx and laryngopharynx before entering the oesophagus
- Hollow muscular tube connecting the pharynx to the stomach- begins at the cricoid cartilage
- Located within the mediastinum, posterior to the trachea and medial to the aorta
- Through esophageal hiatus
- Skeletal muscle or first one-third of length
- Mixture of skeletal and smooth muscle for middle 1/3 of length
- Smooth muscle from inferior one-third of length
- Wall secretes a lubricant

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14
Q

The stomach

A
  • Storage of digested food
  • Mechanical breakdown of ingested food
  • Chemical digestion via acids and enzymes (primarily protein digestion)
  • Ingested food now called chyme
    4 important regions
  • Fundus
  • cardia
  • body
  • pyloric region
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15
Q

Small intestine

A
  • The longest part of the alimentary canal
  • Site of most enzymatic digestion and absorption
  • Receives secretion provided by pancreas and gall bladder (liver)
  • Begins at pyloric sphincter and ends at ileocecal value
  • 3 sub-divisions (duodenum 5% + jejunum 40% + ileum 60%)
  • Innervation: Parasympathetic fibres from vagus nerve; Sympathetic from thoracic splanchnic nerve
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16
Q

Duodenum (C- shaped tube)

A
  • Mixing bowl- chyme with bile and pancreatic secretions
  • Originates from pyloric sphincter
  • Retroperitoneal apart from the most proximal part, which is intraperitoneal
  • Connects to the liver by the lesser omentum
  • Covered by a lining of mucous membrane- protects epithelium from acid chyme
  • Receives digestive enzymes
    Secretions
  • Bile and pancreatic enzymes travel to the duodenum via the main pancreatic and bile duct
  • Sphincters control entry of bile and pancreatic juices
  • Enter the wall of the duodenum at the hepatopancreatic ampulla which opens into the major duodenal papilla
17
Q

Jejunum and Ileum

A

Jejunum
- Important digestive and absorptive functions
- Begins at the duodenal: jejunal junction
- Intraperitoneal suspended by the mesentery proper
Ileum
- Absorption of vitamin B12; salts and all products of digestion that were not absorbed by the jejunum
- Intraperitoneal suspended by the mesentery proper
The ileum ends at a sphincter, the ileocecal value, which controls the flow of material from the ileum into the cecum of the large intestine

18
Q

Circular folds (plicae circulares)

A
  • Transverse ridges of mucosa and submucosa
  • Increase surface for absorption and to slow the passage of food, all parts of the small intestine contain plicae: circular folds of the intestinal lining
  • They appear in duodenum and jejunum prominently and become less common in the ileum
19
Q

Intestinal villi and microvilli

A
  • Intestinal villi are finger-like projections which are located on the mucosal surface of all parts of the intestine and increase the surface area of the intestinal wall
  • Covered by simple columnar epithelium of enterocytes, which absorb digested nutrients
    Microvilli
  • Finger-like projections of plasma membrane on apical surface of columnar epithelial cells
    Increase surface area for absorption and chemical digestion