Digestive System
Musculo Membranous tube
Also called alimentary canal or GI tract
Inside this tube can be considered outside the body
Smooth muscle lined with mucous membrane
Purposed for Digestion & absorbtion of nutrients
Ingestion | Food entering at the mouth |
Digestion | Chewing and enzymes breaking down molecules in a series of changes to break larger molecules into smaller ones to be absorbed |
Movement | Peristalisis = radially symmetrical contraction and relaxation of muscles which propagates in a wave down the muscular tube |
Absorption | Passing of nutrients through wall of digestive tube to reach blood & lymph |
Egestion | Elimination of waste products of digestion |
Broad Path of food
- Mouth
- Pharynx
- Esophagus
- Stomach
- Small intestine
- Large Intestine
- Anus
Accessory Organs à macroscopic or easily visible
Teeth
Salivary Glands
Liver
Gall Bladder
Pancreas
Tongue
Mouth
Vestibule = entryway between teeth & gums (interiorly) and the lips & cheek(exteriorly)
Gingiva = gums, a dense fibrous tissue attached to bone
Superior & Inferior frenulum linguae
small fold of tissue that secures or restricts the motion of tongue
Oral Cavity
Central to teeth and gums
Inferior to hard & soft palate
Superior to tongue and Mandible
Isthmus of fosces goes into oropharynx
Teeth
Crown is above gum line
Covered with enamel
Root extends into gum line
Covered with cemetum
Neck is between root and crown
Teeth are made of dentinge à a bone like substance
Cavity within denting called pulp which contains pulp
The pulp is LCT that supports vessels and nerves
Root Canal is space within the root of a tooth that allows for vessels and nerves to enter and leave
Deciduous teeth à baby teeth
Appear anywhere from 6 months ~ 2 years old on average
When sufficiently calcified it pushes through the gums and the root supplies the force
Lost between 6 years ~ 13 years on average
20 total teeth avg
8 of which are incisors
4 are canines
8 are Molars
Permanent Dentition
32 total teeth avg
Larger than baby teeth
8 are incisors
4 canines
8 Premolars
8 Molar
4 Wisdom Teeth
Tongue
Involved in mastication, swallowing (degulation) and speech
Located on the floor of the mouth
Root connected to hyoid
Tip lies behind lower incisors
Lingual Frenulum attachement
Rough surface due to lingual papillae
Tastes buds at the base
Has mucoid & serous glands which can be mixed
Salivary Glands
3 pairs
produce Saliva & the enzyme Amylase
Parotid
Largest & anterior to external ear
Exocrine gland empties into vestibule
7 cm long
the secretion produced is mainly serous in nature
enters vestibule via Stensen's duct
Submandibular
are a pair of glands located beneath the lower jaw
Empties in the floor of the mouth under the tongue
Enters via Whartons ducts
mixture of both serous fluid and mucus
Sublingual
pair of glands located beneath the tongue
mainly mucous secretions
several tiny excretory ducts release
Pharynx
Common to respiratory & digestive systems
Can elevate & dilate to help move stuff down
3 regions
nasopharynx à behind nose
oropharynx à behind mouth
laryngopharynx à behind larynx
Starts in the skull at about C6
Continues into the esophagus
7 openings
1 mouth
2 nasal
2 tympanic
1 Esophagus
1 Larynx
3 layers
Inner Mucosa
Different types of epithelium depending on location
Fibrous Layer
Fibrous tissues attached to skull
Muscular Layer
Both skeletal and smooth muscle present
Esophagus
23~25 cm long
only has mucoid glands
Rapid movement
Connects laryngopharynx to stomach
Narrowest
Travels through 3 body regions
Neck thorax and abdomen
4 layers
Tunica Mucosa 2 layers too
Linning mucosa
Cells depend on function
Lamina propria
LCT for blood & nerves
Tunica Submucosa
LCT for glands
Tunica Muscularis
Smooth muscle in a circular and longitudinal arrangement
Tunica Serousa (visceral peritoneum)
Largest serous membrane in the body
Stomach 2 openings controlled by sphincters
Cardiac orifice
Pyloric orifice
Features
Lesser Curvature
Greater curvature
Cardia
Pyloris
Body
Fundus
Rugae – internal folds
Outer longitundinal layer
Circular layer
Oblique layer
Gastric glands
Tubular
Zygomenic Cells
Produce pepcinogen
Converts to pepcin with HCl
Pepcin begins digestion of proteins
Oxyentic
Produces the HCl to activate the pepcinogen
Mucous
More prevalent in the cardiac region of the stomach
Produces an Alkaline mucous to protect the body from high acid content
Anterendocrine
Produces gastrin hormone
Gastrin controls production of HCl and Pepcin
Gastrin increase the churning of the stomach
Chyme
a thick fluid mass of partially digested food and gastric secretions passed from the stomach to the small intestine
Small Intestine
Longest at 7 meters long
Begins at pyloric sphincter
Ends at ileocecal valve
Completes digestions & absorbs nutrients
Plicae circularis
The circular folds slow the passage of the food along the intestines, and afford an increased surface for absorption & doesn’t not flatten out
They are covered with small fingerlike projections called villi
Each villus is covered with microvilli
microvilli absorb fats and nutrients from the chyme.
3 Regions
Duodenum
First 25 cm
Supported by Mesentery
Has glands
Jejunum
Next 2 meters
No distinguishing feature to set it apart from rest of small intestine
Ileum
Last 3.5 meters
Joins large intestine
Has Peyer’s Patches
Intestinal glands
At the base of the villi
Produces intestinal juice
Duodenal glands (Brunner’s)
Produces Alkaline mucous for protection at the duodenum
Bile & pancreatic juice enter at the duodenum at the hepaticpancreatic ampula on raise area called duodenal papilla
Large Intestine
1.5 meters long
wider in diameter than small intestine
extends illececal valve
ends at anus
absorbs water
mucous secreting glands for lubrication
parts of the large intestine
Cecum
blind receiving pouch that the small intestine empties into
Appendix
Attached to cecum and is another blind pouch looks like a worm
Colon
Ascending Colon
Up back & to the right
Under the liver
Turns left
Transverse colon
Across the body
Turns downwards
Descending colon
Narrowest part
Sigmoid colon
S shaped
Comes back to the midline
Rectum
Last 20 cm
Anal canal
2~3 cm
anal clumns
Anus
Internal smooth muscular sphincter
External skeletal muscle sphincter
taenia coli
three separate longitudinal ribbons of smooth muscle on the
outside of the ascending, transverse, descending and sigmoid
colons. The teniae coli contracts length wise to produce the
haustra, the bulges in the colon
Liver
Largest gland in the body
2 lobes
larger right side
separating ligament
smaller left lobe
Right lobe has 2 smaller lobes
Quadrate
Transverse fissure between
Caudate
Lobules have chords/strands of hepatic cells that radiate out from central vein
Sinusoids replace typical capillaries
For filtering
The liver receives a dual blood supply from the hepatic portal vein and hepatic arteries
Hepatic portal vein carries venous blood drained from the spleen, GI tract, and its associated organs.
Hepatic arteries supply arterial blood to the liver
Blood flows through the sinusoids and empties into the central vein of each lobule. The central veins combine into hepatic veins, which leave the liver and empty into the inferior vena cava
Central vein à hepatic vein à IVC
Kupffer Cells
specialized macrophages located in the liver lining the walls of the sinusoids that form part of the reticuloendothelial system (RES)
The cords of hepatic cells (hypatocytes) produce Bile
Route of bile
1. canaliculi
2. ducts
3. Right or Left Hepatic Duct
4. Common Hepatic Duct
Joins with the Gall bladders Cystic Duct
5. Common Bile Duct
& Pancreatic Duct from pancreas
6. Hepatopancreatic Duct
7. Ampulla of Vater OR hepatopancreatic ampulla
8. The Sphincter of Oddi
controls the introduction of bile and pancreatic secretions into the duodenum, as well as preventing the entry of duodenal contents into the Ampulla
Gall Bladder
Mucous membrane lined
Muscular sac
Stores and concentrates bile
Smooth muscle contractions move bile out
Pancreas
12~17cm
behind the stomach
in fron the of the IVC, Aorta & left Kidney
Retroperitoneal
Soft oblong tubuloasinar gland
Fits into greater curvature of the stomach
Mixed gland
Partially exocrine & endocrine
Exocrine
Pancreatic juices
Acini cell
Endocrine
Glucagon
Insulin
Few others
Respiratory system to follow
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