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Micro Anatomy > Digestive System > Flashcards

Digestive System Flashcards

1
Q

Gastro-intestinal tract parts

A
  • Pharynx
  • Esophagus
  • Stomach
  • Small intestine
  • Duodenum
  • Jejunum
  • Ileum
  • Large intestine
  • Anus
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2
Q

Accessory structures:

A
  • Oral cavity and
    accessory parts
  • Salivary glands
  • Liver
  • Gall bladder
  • Pancreas
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3
Q

FUNCTIONS OF THE
DIGESTIVE SYSTEM

Ingestion
Chemical
Peristalsis
Digestion
Absorption
Defecation

A

Ingestion
* Taking in food.
* Mechanical:
* Mastication = chewing.
* Co-ordinated movements of the mandible, teeth, lips, tongue.
* Chemical - Serous secretion moistens the food:
* Mucous secretion binds the food bolus ready for deglutition = swallowing.

  • Peristalsis = continuous involuntary muscle movements to move the bolus of food into the stomach.
  • Digestion
  • Breaking food down both physically and chemically.
  • Chyme = semi-digested liquid.
  • Sphincters – serve as “gates” between different parts of the digestive system.
  • Absorption
  • Digestive enzymes from the pancreas and bile from the liver will enter into the duodenum to facilitate fat digestion.
  • Movement of nutrients into the bloodstream.

Defecation
* Rids the body of indigestible waste.

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4
Q

ORAL MUCOSA

A
  • Epithelium – SSNK
  • Exceptions – lips and dorsal tongue (SSK).
  • Epithelium supported by lamina propria – DICT.
  • Many sensory receptors.

Saliva produced by salivary glands:
* Serous secretions
* Mucous secretions
* Seromucous secretions

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5
Q

LIPS

A

Exterior surface (S)
* SSK
* Sebaceous and sweat glands

Transitional zone (V)
* SS
* Occasional sebaceous glands (no sweat glands or hair follicles).

  • Interior (O)
  • SSNK
  • Lamina propria
  • Skeletal muscles (M)
  • Salivary glands (G)
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6
Q

TONGUE

parts anterior and posterior

A
  • Muscular organ covered by oral mucosa.
  • Solid mass of skeletal muscles
    – multidirectional orientation of muscle fibers.

Specialized in:
* Manipulating of food
* Sensory function of taste
* Speech
* Divided into anterior 2/3 and posterior 1/3 by sulcus terminalis

Anterior tongue is made up of papillae:
* Filiform
Threadlike bristlesm-Tastebuds absent
* Fungiform
Mushroom- shaped- Tastebuds present
* Foliate
Leaf-life- Tastebuds present
* Circumvallate
Serous glands at the base of papillae
Numerous tastebuds

Posterior tongue is composed of:
* SSNK epithelium
* Lymphoid tissue
* Waldeyer’s ring – made up of lingual tonsil, pharyngeal tonsil and palatine tonsils

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7
Q

SALIVA

A

Thin watery suspension.
* Secreted by:
* Serous cells-Enzymes, mucous, inorganic
ions, antibodies.
* Mucous cells -Mucinous substances.

Functions:
* Cleansing action on the teeth.
* Moistens and lubricates food during mastication and swallowing.
* Dissolves certain molecules so foods can be tasted.
* Initiates chemical digestion of starches with the help of an enzyme called salivary amylase.

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8
Q

SALIVARY GLANDS

Parotid glands
* Submandibular glands
* Sublingual glands

A

PAROTID GLANDS
Morphology: Compound acinar.
Secretion type: Mostly serous substances.

SUBMANDULAR GLANDS
Morphology: Compound tubuloacinar.
Secretion type: Serous and mucous
substances

SUBLINGUAL GLANDS
Morphology: Compound tubular
Secretion type: Mostly mucous substances

  • all have Compound glands with lobules separated by septae (made up of collagen fibers).
  • With branching ducts
  • Intralobular ducts Ducts “within the lobes”
    smaller diameter
  • Interlobular ducts Ducts “between the lobes” Larger diameter.
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9
Q

SALIVARY SECRETORY UNIT

Serous cells
Mucous cells
Myoepithelial cells

A

Serous cells
* Secrete serous substances.
* Shaped like pyramids.
* Nuclei are round

Mucous cells
* Secrete mucous substances.
* Shaped like pyramids.
* Nuclei are flat.

Myoepithelial cells
* Located on the surface of the secretory units.
* resemble smooth muscle cells.
* As myoepithelial cells contract, they press on the acinus, releasing secretory product into the duct of the gland.
* They lie between the basal lamina and the epithelial cells of the acini.

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9
Q

LIVER

A
  • Largest gland in the body
  • Lies beneath the diaphragm.
  • Lobes: left and right separated by falciform ligament.
  • Functional unit: Hepatocytes.
  • Exocrine function: Bile formation and secretion.
  • Endocrine function: Production of some plasma proteins and hormones.
  • Detoxification.
  • Metabolism of food (fat,
    carbohydrate and protein).
  • Storage of iron, glycogen and vitamins A, B12 and D.
  • Site of fetal hematopoiesis
  • Glisson’s capsule – DICT.
  • Lined by mesothelium – simple cuboidal.
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10
Q

HEPATOCYTES

A
  • Functional units of the liver.
  • Large, polyhedral cells with round nuclei and prominent nucleoli; sometimes exhibiting binucleation (2 nuclei).
  • Structures in between the hepatocytes are sinusoids.
  • Presences of lipofuscin (wear and tear pigment).
  • Supported by reticular connective tissue.
  • Store glycogen.
  • Form bile.
  • Hepatocytes + phagocytic Kupffer cells - remove bacteria and worn out RBCs from the blood.
  • Absorb nutrients and secrete products into the bloodstream.
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11
Q

CELLS LINING THE SINUSOIDS in the liver

A
  • Endothelial cells : squamous’ cells lining the endothelium
  • Kupffer cells
  • AKA Reticuloendothelial cells - monocytemacrophage defense system + removal of old RBCs
  • Stellate/Ito cells or hepatic lipocytes
  • Produce lipid droplet with vitamin A and produce ECM + collagen
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12
Q

LIVER LOBULES

A
  • Pentagon or hexagon shaped cylinder made of hepatocytes arranged as thin plates separated by sinusoids.
  • Both hepatocytes and sinusoids radiate towards the center of the lobule.
  • At the center of each lobule is a centrilobular vein/central.
  • Portal triad at each corner of the lobules:
  • Bile duct
  • Portal vein
  • Hepatic artery
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13
Q

GALL BLADDER

A
  • Muscular sac like structure.
  • Hollow organ
  • Stores, concentrates and releases bile that the liver produces.
  • Carries bile into the small intestine to aid in digestion
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14
Q

HISTOLOGICAL FEATURES of the gall bladder

A
  1. MUCOSA = Epithelium + Lamina propria.
    * Epithelium: Simple columnar with microvilli.
    * Lamina propria: LOCT.
    * Mucosa has infoldings called rugae.
  2. SUBMUCOSA
    * LOCT, vascular, elastin and collagen fibers, lymphatic vessels.
  3. MUSCULARIS EXTERNA
    * Smooth muscles in all directions, not layered.
  4. SEROSA/ADVENTITIA
    * LOCT.
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15
Q

PANCREAS

A

Large gland ~15cm long.
* Located in the abdomen in the curve of the duodenum.

Has both exocrine and endocrine functions:

EXOCRINE
* Majority of the pancreas.
* Cells of acinar units secrete digestive enzymes and pancreatic juices.
* Secretions drain into a duct system.
* Morphology: Compound acinar
* Lobulated by CT septae
* Intralobular (within the same lobule) & interlobular ducts (between lobules).

ENDOCRINE.
* Cells secrete hormones essential for control of carbohydrate metabolism.
* Secretions go directly into the capillaries.
* Islets of Langerhans (pancreatic islets)
* Morphology: Clump and cord

Cells:
* Alpha cells – glucagon.
* Beta cells – insulin.
* Delta cells.
* Polypeptide cells.

16
Q
  • Three components of mucosa and its transitional changes
A
  • Surface epithelium: either SSNK or simple columnar types.
  • Glandular epithelium: either simple branched tubular or simple tubular.
  • Lamina propria
  • LOCT supporting the epithelium.
  • Lymphoid tissues found here – MALTs (GALTs)
  • Muscularis mucosae
  • Narrow band of smooth muscles.
  1. Gastroesophageal junction:
    * Between esophagus and stomach
    * SSNK → Simple columnar (squamocolumnar junction).
  2. Gastroduodenal junction:
    * Between stomach and duodenum.
    * Simple branched tubular → Simple tubular.
  3. llecocecal junction:
    * Between ileum and cecum
    * With villi → without villi.
  4. Rectoanal junction:
    * Between rectum and anus
    * Simple tubular → SSK.
17
Q

SUBMUCOSA

A
  • “Just beneath the mucosa”.
  • LOCT
  • Thick bundles of collagen fibers.
  • Many blood vessels + lymphatics + nerves.
  • Meissner’s plexus (nerves)
  • Innervate the muscularis mucosa and mucosal glands.
  • Submucosal glands
  • Compound tubular glands of the esophagus and duodenum.
18
Q

MUSCULARIS EXTERNA

A
  • Inner and outer layers of smooth or skeletal muscles.
  • Exceptions:
  • Upper third of the esophagus has two layers of skeletal muscles.
  • Stomach has three layers of smooth muscles.
  • Auerbach’s plexus (nerves)
  • Located between the muscle layers.
  • Provides innervation to these smooth muscles.
19
Q

SEROSA/ADVENTITIA

A
  • AKA serous membrane.
  • The outermost layer
  • LOCT - supporting blood vessels, nerves and adipose tissue.
  • Serosa
  • Responsible for covering external surfaces of the organs that are faced with the body cavities.
  • Adventitia
  • Responsible for attaching the organs to the surrounding tissues.
20
Q

ORGANS OF THE GIT

A
  • Pharynx
  • Esophagus
  • Stomach
  • Small intestine
  • Large intestine
  • Appendix
  • Anus
21
Q

ANATOMY OF PHARYNX

A
  1. Nasopharynx
    * Not part of the digestive system.
  2. Oropharynx
    * Posterior to the oral cavity.
    * Involved in swallowing.
  3. Laryngopharynx
    * Below the oropharynx and connected to the esophagus
  • Serves as passageway for food and air.
  • Passageway for food:
  • Mouth → oropharynx → esophagus → stomach.
  • Food is propelled to the esophagus by two skeletal muscle layers:
  • Inner longitudinal layer
  • Outer circular layer
  • Food movement is facilitated by peristalsis

Mucosa
* Epithelium – SSNK.
* Lamina propria – LOCT + increased amount of elastin fibers

  • Submucosa- Absent.

Muscularis externa
* Skeletal type – striated, voluntary (SV).
* Inner longitudinal
* Outer circular

  • Outer layer – buccopharyngeal fascia
  • LOCT + nerves + blood vessels
22
Q

ANATOMY OF ESOPHAGUS

A
  • Conducts food by peristalsis.
  • Passageway for food only epiglottis cartilage flaps up or down for eating and breathing passageways
  • First segment of the digestive tract.
  • Has 3 regions:
    1. Upper 3rd
    2. Middle 3rd
    3. Lower 3rd
  • Has 2 sphincters:
    1. Upper esophageal sphincter – skeletal muscles
    2. Lower esophageal sphincter – smooth muscles

Mucosa
* Protective type.
* Epithelium – SSNK.
* Lamina propria – LOCT
* Muscularis mucosa – skeletal/smooth muscle.
* Lymphoid tissues (MALTs).

Submucosa
* Mucous secreting esophageal glands (compound tubular)
* LOCT
* Meissner’s plexus

Muscularis externa
* 2 layers:
* Inner circular
* Outer longitudinal
* Skeletal – upper 3rd
* Skeletal + smooth – middle 3rd
* Smooth – lower 3rd
* Auerbach’s plexus.

  • Adventitia
  • LOCT.
23
Q

GASTROESOPHAGEAL
JUNCTION AKA: Squamocolumnar
junction.

A
  • Food - Enters at the lower esophageal sphincter.
  • Empties into the small intestine at the pyloric sphincter (valve).
  • Stomach is located on the left side of the abdominal cavity
  • Abrupt change in mucosa
    from SSNK (esophagus) →simple columnar (stomach).
  • This junction provides a physiological sphincter to prevent reflux
  • Affected by gastric reflux.
  • If metaplasia occurs – Barrett’s esophagus.
  • High risk for developing dysplasia and invasive carcinoma.
24
Q

STOMACH

A
  • Muscular storage tank for food.
  • Site of food breakdown.
  • Chemical breakdown (pepsin) of protein begins.
  • Delivers chyme (processed food) to the small intestine.
  • Interior is acidic.
  • Rugae – internal folds of the mucosa.
  • Allows for distention.
  • External regions; Less and greater curvature
  • Regions of the stomach:
    1. Cardia - length of gastric pits are the same as the cardiac glands - coiled secreting mucous
    2. Fundus and Body- 1/4 are composed of gastric pits with straight tubular glands secreting mucous HCL and pepsin. Composed of stem, mucous, parietal, chief and enteroendocrine cells
    4. Pylorus- deep gastric pits. glands are branched and coiled - mucus secreting
  • Two sphincters
    1. Lower esophageal sphincter
    2. Pyloric sphincter formed by the musculature muscle in pylorus
25
Q

MICROANATOMY OF THE
STOMACH

A

Mucosa
* Secretory type.
* Glandular epithelium – Gastric pits
* Simple branched tubular going from surface into the underlyinglamina propria.
* They branch downwards to become gastric pits.

Surface epithelium of gastric pits
*Simple columnar secreting mucous to protect the stomach lining from the acidic environment.
* Secretory cells in the gastric glands vary in each region of the stomach

  • Lamina propria – LOCT + intraepithelial lymphocytes.
  • Muscularis mucosae – smooth muscles

Submucosa
* LOCT + Meissner’s plexus

Muscularis externa
* Inner – oblique
* Middle – circular
* Outer – longitudinal
* Esophageal & pyloric sphincters – circular smooth muscle fibers.
* Auerbach’s plexus in between the layers of interdigitating muscles.

  • Serosa/Adventitia
  • LOCT
26
Q

GASTRODUODENAL JUNCTION

A
  • Functions:
  • Controls the movement of the stomach contents into the duodenum.
  • One-way gate guard.
  • Ring of smooth muscles at the pyloric sphincter.
  • Glandular epithelium
  • From Simple branched tubular (secretory) to Simple tubular (absorptive)
27
Q

SMALL INTESTINE

A
  • Muscular, hollow tube extending from the pyloric sphincter to the ileocecal valve.
  • Coiled loops in abdominal cavity
  • major digestive organ.
  • Site of nutrient absorption into the blood.

3 fluids to aid in digestion:
* Intestinal juice from the walls of the intestine.
* Pancreatic juice from the pancreas.
* Bile from the liver.

Duodenum -Brunner’s gland
Jejunum - increased plicae circularis.
Ileum-Peyer’s patches

28
Q

MUCOSAL MODIFICATIONS THAT
INCREASE SURFACE AREA

A
  • Microvilli
  • Microscopic projections of the cell plasma membrane (creates a brush border appearance).
  • Villi
  • Finger-like structures formed by the mucosa.
  • Each villus contains lacteals (lymphatic capillaries).
  • Lined by enterocytes – absorptive surface cells (simple columnar with microvilli cells).
  • Plicae circularis – circular folds
  • Deep folds of the mucosa and submucosa.
29
Q

MICROANATOMY OF
SMALL INTESTINE

A

Mucosa
* Absorptive type.
* Surface epithelium – absorptive cells: enterocytes.
* Simple columnar with goblet cells and microvilli.
* Goblet cells – unicellular glands that secrete mucous. increasing from duodenum to rectum.

  • Intestinal glandular epithelium
    Crypts of Lieberkuhn
  • Simple tubular - lined by simple columnar with goblet cells and microvilli.
  • At the bottom of the crypts are Paneth cells –eosinophilic granules that act as anti- microbial agents.
  • Enteroendocrine cells –hormone secreting cells
  • Intestinal glands are supported by lamina propria – LOCT + intraepithelial lymphocytes.
  • Muscularis mucosa – smooth muscles.
  • MALTs (GALTs) – throughout the small intestine. Peyer’s patches

Submucosa
* LOCT
* Meissner’s plexus
* Brunner’s gland only found in duodenum
* Compound tubular.
* Secretes alkaline mucins.

Muscularis externa (same in small and large intestine)
* Inner circular muscles
* Outer longitudinal muscles
* Auerbach’s plexus

Serosa/Adventitia
* LOCT.

30
Q

LARGE INTESTINE

A
  • Resorption of water and mineral ions.
  • Formation and temporary storage of faeces.
  • Bacterial fermentation of indigestible materials -ileocecal sphincter to external anal sphincter.
  • No plicae circularis, no villi.
  • Presence of taeniae coli
    • 3 longitudinal bands of muscularis externa.
  • Presence of haustra coli.
    * Small pouches in the wall of the large intestine caused by sacculation.
31
Q

ANATOMICAL DIVISIONS OF
THE LARGE INTESTINE

A

Cecum
* First 5-8cm of the large intestine.

Colon
* Ascending colon
* Transverse colon
* Descending colon
* Sigmoid colon

Rectum
* Last 7-8 inches of the large intestine – narrows to become the anal canal.

Anal canal
* Terminal inch of the rectum.
* change from simple columnar to SSK

32
Q

MICROANATOMY OF
LARGE INTESTINE

A

Mucosa
* Absorptive type
* Surface epithelium – absorptive cells: enterocytes.
* Simple columnar with goblet cells and microvilli.
* Goblet cells – more numerous in the large intestines – provides lubrication for the fecal material passing through.

  • Intestinal glandular epithelium
  • Crypts of Lieberkühn – very straight.
  • Simple tubular.
  • Reduced number of enteroendocrine cells.
  • NO PANETH CELLS.
  • NO VILLI.
  • NO PLICAE CIRCULARIS.

-Lamina propria – LOCT+intraepithelial lymphocytes.

-Muscularis mucosa – smooth muscles.

Submucosa
* LOCT
* Meissner’s plexus

  • Muscularis externa
  • Inner circular
  • Outer longitudinal – segregated into 3 longitudinal bands (TAENIAE COLI) causing permanent segmentations of
    the large intestine, called HAUSTRA COLI.
  • Auerbach’s plexus.

Serosa/Adventitia
* LOCT.

33
Q

APPENDIX

A
  • Worm-like tubular organ – attached to cecum
  • Immune function; breeding ground for normal flora of the large intestine.
  • Histological features resemble large intestine.
  • Presence of lymphoid tissues in the mucosal layer.
  • Lymphoid follicles in the walls of the appendix – with germinal centers.
  • Muscularis externa –
  • Inner circular
  • Outer longitudinal muscles.
34
Q

RECTOANAL JUNCTION

A
  • Squamocolumnar junction.
  • Rectum narrows to become anal canal.
  • change in epithelium From Simple columnar to SSK.
  • SSK undergoes gradual transition to skin containing sebaceous glands and sweat glands
35
Q

ANUS

A
  • Terminal end of the intestinal tract.
  • External anal sphincter. Formed by skeletal muscle under voluntary control.
  • Internal anal sphincter. Formed by smooth muscles under involuntary
    control.
  • These sphincters are normally closed except during defecation.

Micro Anatomy (14 decks)

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