Digestive System

Ingestion

Complex foods taken into the GI tract

Motility

A number of GI movements resulting from muscular contraction

Digestion

Group of processes that break complex nutrients into simpler ones

Secretion

ØRelease of digestive juices and hormones that facilitate digestion

Absorption

ØMovement of digested nutrients into the internal environment of the body

Regulation

ØNeural, hormonal, and other mechanisms that regulate digestive activity

called alimentary canal or gastrointestinal (GI) tract

Irregular tube

˜Principle structure of digestive system: Irregular tube called alimentary canal or gastrointestinal (GI) tract and accessory organs of digestion

˜Transfers nutrients, water, and electrolytes from food into the body’s internal environment.

•Motility

•Secretion

•Digestion

•Absorption

 The digestive system performs four basic digestive processes:

common hepatitic duct

alimentary canal

another name for gastrointestinal tract

cystic duct

§Salivary Glands.

§Liver.

§Gall Bladder.

§Pancreas.

Accessory Organs:

common bile duct

roof

Formed by hard palate and soft palate 

hard palate

parts of maxillary and palatine bones

soft palate,

arch-shaped muscle separating mouth from pharynx

˜Uvula

: Downward projection of soft palate

Floor

˜Formed by tongue and its muscles

Papillae

˜Small elevations on mucosa of tongue

Lingual frenulum

˜Fold of mucous membrane that helps anchor tongue to floor of mouth

sensory analysis, mechanical processing, lubrication, limited digestionm

Accomplishments in the Oral Cavity

•Crown

•Neck

•Root

ØThree main parts of teeth

enamel

 which covers the crown, is hardest tissue in body

20 teeth

deciduous or baby teeth

32

permanent teeth #

6 ; 17 and 24

ØAverage age to cut first permanent tooth ___ years old; set complete usually between _________years old

6; 30 

ØAverage age cutting first tooth ___ months old; set complete at ___ months old

Serous-type saliva:

ØWatery and contains enzymes (salivary amylase) but no mucus

•Produced by serous-type secretory cells

Mucous-type saliva

ØThick, slippery and contains mucus but no enzymes

•Lubricates food during mastication

•Produced by mucus-type secretory cells

One pair of parotid glands

 One pair of sublingual glands

 One pair of submandibular glands

- 3 pairs of salivary glands

˜Parotid glands

ØLargest salivary glands

ØProduces serous type saliva

ØMumps (viral infection):

Infection of parotids

˜Submandibular glands

ØMixed gland: Produces both serous-type and mucous-type saliva

ØLocated below mandibular angle

˜Sublingual glands

ØProduce only mucous-type saliva

Approximately 1 Litre/day

pH 6.0-8.0

Hypotonic

99% H₂O

1% solutes:

•     Electrolytes: (ions such as Na⁺, K⁺, Cl^-, PO4^{-2 (phosphate)}, HCO_{3 (bicarbonate)}^, thiocyanate).

•  Metabolic wastes: (urea, uric acid)

•  proteins:

Composition of Saliva

Mucins

these are glycoproteins secreted and converted into mucus

Salivary amylase

starts digestion of carbohydrates in the mouth

  Salivary lipase:

starts digestion of lipids in the mouth

Lysozyme

this is antibacterial enzyme

IgA

these are antibodies that prevent antigens from attaching to mucus   membrane

Lactoferrin

: this is a protein that inhibits growth of many microorganisms by removing iron

moistens and lubricates food, digestion of polysacchardies by  amylase, dissolves food, antibacterial actions

functions of saliva 

Pharynx

˜is a tubelike structure made of muscle and lined with mucus membrane.

Pharynx

˜is a tubelike structure made of muscle and lined with mucus membrane.

Pharynx

˜A common passageway for solid food, liquids, and air

ØNasopharynx

ØOropharynx

ØLaryngopharynx

˜Three anatomic components

Oropharynx

˜most involved segment in digestive process of swallowing or deglutition [pharynx]

cerebrum

voluntary

brainstem

“deglutition center” of ___________ (involuntary)

Pharynx

Food passes through oropharynx and laryngopharynx to esophagus

Pharyngeal muscles

_________ assist in swallowing

Swallowing

is the movement of food from the mouth through the pharynx and esophagus into the stomach.

- The oral phase (buccal phase), Pharyngeal and esophageal phases (involuntary):

3 phases of swallowing

the swallowing center

- The respiratory center of the medulla is directly inhibited by __________ for the very brief time that it takes to swallow.

The upper esophageal sphincter (UES)

relaxes and the pharyngeal muscles contract to push the bolus of food down into the esophagus.

esophagus

˜is a muscular, mucus-lined tube.

Esophagus

˜It is about 25 cm (10 inches) long.

˜Upper esophageal sphincter (UES)

ØHelps prevent air  from entering tube during respiration

ØLES

normally prevents backflow of acidic stomach contents.

LES or cardiac sphincter

ØFood enters stomach by passing through ______________

Stomach

˜lies in the upper part of the abdominal cavity.

˜fundus, body, and pylorus.

Three divisions of stomach:

large sausage

ØExpands after large meal; about size of ______________ when empty

Pyloric sphincter

˜muscle closes opening between pylorus (lower part of stomach) and duodenum

pylorus

(lower part of stomach)

pylorus 

gatekeeper

fundus

body

mucus pespinogen and HCl

what does body secret 

antrum

gastrin, pepsinogen, mucus

what does antrum secrete

stomach wall

many smooth msucle fibers; produce churning movements

stomach lining

mucuos membrane; many microscopic glands that secrete gastric juice and hcl into stomach

persitalsis 

churning movements 

simple columnar epithelial cell

cell the lines the mucosa 

pepsinogen

cheif cell secretes waht

mucous

mucous cells secrete what

HCl and intrinsic factor

parietal cell secretes what

secretes gastrin

enteroendocrine cell

mucosa— submucosa——muscularis—-serosa

order from inside to outch

§Bulk storage of undigested food

§Mechanical digestion due to churning (agitate or turn)

§Chemical Digestion due to acid and enzymes

§Production of intrinsic factor (IF)

§Needed for absorption vitamin B₁₂

§Very little absorption

Accomplishments in the Stomach

2-3L a day 

gastric juice 

•HCl

•

•Activates Pepsinogen

•Aids Iron Absorption

•Kills Bacteria

•Pepsinogen

•Initiates Protein Digestion

•IF

•Required for Vit B₁₂ Absorption (in terminal Ileum)

3

musuclaris of stomach how many layers

lamina propia

connective tissue layer in the mucosa

Small Intestine wall 

ØContains smooth muscle fibers that contract to produce peristalsis and segmentation movements

Villi

microscopic finger-shaped projections from surface of mucosa into intestinal cavity

Villi

contain blood and lymph capillaries 

small intestine lining

ØMucous membrane with villi

plicae

– folds which are covered in villi: finger-like projections

plicae

•are covered in microvilli

•are responsible for the absorption of nutrients into the body

plicae

•contain blood vessels and lacteals

•blood vessels

collect sugar and amino acids

lacteals

•collect lipids

Intestinal Wall:

•greatly increase the surface area for absorption

longitudinal and circular muscle

muscularis layers in small intestine 

Small Intestine

•Is 3 m to 11 m in length