Anatomy & Physiology II Misericordia University Digestion Anatomy & Physiology II Tony Serino, Ph.D. Biology Department Misericordia University

Digestion The reduction through mechanical and chemical means (hydrolysis) of complex food substances into simple monomers and their absorption into the internal environment.

Functions of Digestive System Motility(Propulsion) Ingestion –food enters tract Mastication -chewing Deglutition -swallowing Transportation through tract (peristalsis) Mixing Egestion (Defecation) Secretion Endocrine and Exocrine secretions Digestion mechanical and chemical breakdown of food Absorption Passage of food particles from external to the internal environment

Major Organs of System

Accessory Organs Teeth

GI Tract Development Post-gastrula Late Gastrulation Pylorus

Basic Histology of Digestive Tract (Auerbach’s) (Meissner’s) (LOCI)

Tube Movements Peristalsis Segmentation

Retroperitoneal Position

Peritoneal Cavity Lesser Peritoneal Cavity Greater Peritoneal Cavity

Mesenteries

Mesenteries

Control of Overall GI Tract Activity

Oral Cavity (sagittal) Mucosa: Stratified Squamous epithelia Muscularis: Skeletal muscle overlying bone Functions: Ingestion Mastication Hydration of food Begins chemical digestion Formation of bolus

Oral Cavity (anterior) (Red Margin)

Tongue Functions: mixing, speaking, and swallowing Intrinsic and extrinsic muscles Foliate papillae Three layers of skeletal muscle.

Major Salivary Glands Secrete saliva –mixture of water, mucus, electrolytes, antibodies and enzymes. Enzyme is salivary amylase which breaks down starches.

Teeth Function: mastication (chewing and grinding of food into a paste consistency)

Primary Dentition

Adult (Permanent) Dentition

Tooth Anatomy Odontoblasts –secrete dentin Ameloblasts –secrete enamel

Pharynx Function: deglutition Mucosa: Str. Squamous Muscularis: Skeletal

Esophagus Function: Deglutition Two sphincters: upper and lower esophageal sphincters (lower is physiological only) Retropleural position (therefore, covered by adventitia) Mucosa: stratified squamous with many mucus glands (esophageal glands) Muscularis: changes from skeletal to smooth muscle

Esophagus Histology

Deglutition (Swallowing)

Deglutition (cont’d)

Stomach (cadaver) J-shaped muscular pouch Receives bolus and produces chyme Liquefies food by mixing it with HCl and vigorous churning Low pH stops amylase activity, but secretes pepsinogen (pepsin) that begins break down of proteins Absorbs little except imbibed water, electrolytes, and some drugs (ie. alcohol and aspirin)

Stomach Anatomy Mucosa: Muscularis: Has three layers simple columnar folded into rugae No villi Openings leading to gastric pits and glands Muscularis: Has three layers

Rugae of Stomach Temporary longitudinal foldings of the mucosa

Stomach Histology

Gastric Gland

Regulation of Gastric Juice

Gastric Emptying

Gastric Emptying

Inhibition of Gastric Emptying

Small Intestine

Small Intestine

Duodenum and Accessory Organs

Small Intestine Structures to Increase Surface Area Plica Circularis Villi Long Length of SI

Small Intestine Histology

Histology Changes in Intestine

Villi Histology

Large Intestine (x-ray)

Large Intestine (Colon)

Large Intestine Histology

Anal Canal

Defecation Reflex

Upper Abdominal XS

Liver

Liver (inferior surface)

Liver Lobule

Bile Ducts

Bile and Pancreatic Ducts

Duodenal Papilla

Secretion of Bile

Pancreas

Pancreas Histology

Pancreatic Acinus

Exocrine Secretions of Pancreas

Secretion of Pancreatic Juice

Micelle Formation (Emulsifying Fat)

Fatty Acid Absorption

Amino Acid Absorption

Food Digestion Summary

Food digestion Summary