Digestive System

Topics: Liver, Digestion, Digestive system Pages: 17 (3761 words) Published: July 27, 2013
The Digestive System
We need food for cellular utilization: !nutrients as building blocks for synthesis !sugars, etc to break down for energy most food that we eat cannot be directly used by the body !too large and complex to be absorbed !chemical composition must be modified to be useable by cells digestive system functions to altered the chemical and physical composition of food so that it can be absorbed and used by the body; ie Functions of Digestive System: 1. physical and chemical digestion 2. absorption 3. collect & eliminate nonuseable components of food

Anatomy of the Digestive System
organs of digestive system form essentially: a long continuous tube open at both ends ! alimentary canal (gastrointestinal tract) mouth!pharynx!esophagus!stomach! small intestine!large intestine attached to this tube are assorted accessory organs and structures that aid in the digestive processes salivary glands teeth liver gall bladder pancreas mesenteries The GI tract (digestive system) is located mainly in abdominopelvic cavity surrounded by serous membrane = visceral peritoneum this serous membrane is continuous with parietal peritoneum and extends between digestive organs as mesenteries ! hold organs in place, prevent tangling

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Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2010.4

Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2010.4

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The wall of the alimentary canal consists of 4 layers:
outer

is suspended from rear of soft palate blocks nasal passages when swallowing tongue lines ventral border of mouth cavity is skeletal muscle covered with mucous membrane contains taste buds frenulum is thin fold of mucous membrane on ventral surface of tongue that anchors the tongue to the floor of the mouth short frenulum ! “tongue tied”

serosa:
visceral peritoneum, mainly fibrous and areolar CT with some pockets of adipose CT

muscularis
several layers of smooth muscle

submucosa
blood vessels, lymphatic vessels, nerves, connective tissue
inner

mucosa:
small band of muscle tissue, muscularis mucosa mucus membrane lining contains goblet cells that secrete mucous for protection

Teeth two sets deciduous (=baby teeth) permanent teeth each tooth has a crown (above gum) neck is where crown, gum and root meet root (below gum) imbedded in socket gingivitis = inflammation of gum surrounding teeth; can lead to 3

Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2010.4

these layers are modified within various organs
! some have muscle layers well developed ! some with mucous lining modified for secretion of digestive juices ! some with mucous lining modified for absorption

(20) begin at 6 months; shed 6-13 yrs (32)

1. Mouth (Buccal Cavity, Oral Cavity) bordered above by hard and soft palate forms partition between mouth and nasal passages

uvula
Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2010.4

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periodontal disease

Salivary Glands 3 Pairs of salivary glands: sublingual submandibular parotid largest, below ears mumps = acute infection of parotid gland

kinds of teeth modified for specific functions incisors – 4+4; cut, knip canines – 2+2; holding onto prey premolars – 4+4; cutting, crushing molars – 6+6; chewing, grinding, crushing each tooth is composed of several layers: enamel very hard outer surface on upper exposed crown only resists bacterial attack cannot regenerate if damaged

secrete saliva (enzymes and mucous for digestion) 2. Pharynx (throat) already discussed 3. Esophagus collapsible tube ~ 10” long extends from pharynx to stomach !gets food through thorax to abdominal cavity

dentin
below enamel less hard, similar to bone matrix decays quickly of enamel is penetrated

pulp
living portion of tooth consists of blood vessels, nerves

posterior to trachea and heart pierces diaphragm uses peristalsis to move food to stomach ! can swallow upsidedown
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