Unit 3: Digestive & Urinary Systems:

Provides nutrients for cell maintenance and growth, works with other tissues that don’t have contact with the outside environment.

What is the function of the urinary system?

begin at oral cavity, pharynx, esophagus, stomach, small intestine, and large intestine. 

What organs are involved in the digestive system?

GI Tract

long muscular tube, lined with permanent ridges & folds (increases surface area)

Mesentery

double sheet of peritoneal membrane

Function of Mesentery

Provides access for blood vessels, nerves, and lymphatics, stabilizes organs & prevents entanglement of intestines

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How many layers does the digestive tract have?

Mucosa

inner lining, glands that produce mucus & other products 

Submucosa

layer of Irregular connective tissue for blood vessels, lymphatics, nerves

Muscular Externa

layer of smooth muscle, alter shape of lumen, help move food along tract

Serosa

layer, attaches tract to adjacent structures

Multi Unit Smooth Muscle

type of smooth muscle where each cell can be connected to more than one neuron, instant movement, found in the eye

Visceral Smooth Muscle

type of smooth muscle where the muscle is not in direct contact with motor neurons, movement is wave like, found in GI tract

Motility

the way in which the GI tract moves

Peristalsis

propels contents forward

Segmentation

Mixes contents up

Local factors, Neural control, & Hormonal Control

What are the regulators of Digestion?

Local Factors

Primary stimulus for digestive activities:

• EX: change in PH of lumen, distortion, presence of chemicals

Neural Control

1. Short reflexes: triggered by receptors in the tract walls

2. Long Reflexes: higher level of control, involves neurons of CNS, control peristalsis

Hormonal Control

Involves 18+ hormones that affect digestion, hormones are produced by enteroendocrine cells

Digestion

Chemical breakdown of large molecules into small building block molecules

Ingestion

Occurs when solid food & liquid enter oral cavity 

Location: oral cavity

Mechanical processing

involves crushing & shredding of food in the oral cavity & mixing/ churning in stomach

Location: Oral cavity 

secreation

release of water, acids, enzymes, buffers, & salts

location: stomach / small intestine

Absorption

Movement of organic molecules, electrolytes, vitamins, & water across the digestive epithelium & into the interstitial fluid 

location: small intestine

Compaction

progressive dehydration of indigestible materials & organic wastes prior to elimination

location: large intestine

Ingestion/mechanical processing, digestion, secretion, absorption, compaction/defecation 

What are the major steps of digestion?

Oral Cavity

lined by oral mucosa, no absorption of nutrients, digestion of carbs & lipids begins here

Hard Palate

Palatine processes of maxillary bones & horizontal plates of palatine bone

Soft Palate

Muscular region posterior to hard palate 

Hard & soft palate

What parts make up for superior boundary?

cheeks & lips

What parts make up the anterior & lateral Boundaries?

cheeks

form lateral walls of oral cavity, supported by pads of fat & buccinator muscle 

uvula, tongue, palatine & lingual tonsils

What parts make up the Posterior boundary?

uvula

prevents food from entering pharynx, swings upward during swallowing to prevent food from entering nasopharynx

Crown of tooth

projected portion of teeth

Neck of teeth

marks boundary between crown & root of tooth

Root of Teeth

part of tooth that sits in bony socket called alveolus 

dentin

hard matrix of tooth, contains no cells, makes of majority of tooth

Pulp cavity

interior chamber of tooth

Occlusal Surface

ridges of tooth used for crushing/ chewing 

Enamel

covers dentin of tooth, hardest biologically manufactured substance 

Gingival Sulcus

shallow groove at neck of tooth, epithelial layer to block bacteria

Peridontal Ligament

connects root of tooth to alveolar bone

Root canal

tunnel for blood vessels and nerves in teeth 

Incisors

teeth used for clipping / cutting

Cuspids

teeth used for tearing / slashing 

Bicuspids

teeth used for crushing, mashing & grinding

Molars

teeth used for grinding & crushing

Primary Dentition

20 teeth, milk teeth or baby teeth

Secondary Dentition

32 teeth, wisdom teeth can be present, adult teeth

Gingivitis

inflammation of gingivae, weakened attachment causes bacterial infection & erosion of gums

Tooth Decay

due to bacteria on teeth, results in plaques

Pharynx

membrane lined cavity behind nose and mouth, continuous with esophagus, has 3 parts: nasopharynx, oropharynx, and laryngopharynx.

Esophagus

conveys food & liquids to stomach, hollow & muscular, narrow at top & widens as you go down, goes through esophageal hiatus of diaphragm 

Upper Esophageal Sphincter

prevents air from entering the esophagus

Lower Esophageal Sphincter

located at the end of the esophagus, prevents backflow of stomach contents

Swallowing

complex process, initiated voluntarily but proceeds automatically 

Buccal Phase

phase where compression of bolus against hard palate occurs, tongue forces bolus into oropharynx

Pharyngeal Phase

phase when muscle contractions in the pharyngeal muscles move bolus into esophagus, larynx elevated & epiglottis folded

Esophageal Phase

phase where bolus is forced into esophagus, peristalsis moves food towards stomach, 9 second travel time

1. Storage of ingested food

2. Digestion

3. Disruption of chemical bonds in food through the action of acid & enzymes

What are the functions of the stomach

Cardia, Fundus, Body, Pylorus 

What are the 5 parts of the stomach?

Cardia

region where esophagus empties into stomach, secretes mucus to protect esophagus

Fundus

dome shaped top of stomach

Body of Stomach

largest portion of the stomach, large mixing bowl leads to churning of food 

Pyloris Antrum

inferior part of stomach, J shaped

Pyloric Sphincter

connects pylorus to duodenum of small intestine

Rugae

folds of the stomach, allows stomach to expand 

Longitudinal, Circular, Oblique

What are the layers of muscle in the stomach?

Parietal Cells

cells that make hydrochloric acid (HCL)

G Cells

Cell that make hormones

Chief Cells

cells that make pepsinogen

HCL 

made from the Co2 and H20 made into carbonic acid, which separates into bicarbonate and H+. the bicarbonate leaves the cell and CL- comes in, the H+ and CL- exit into the lumen of the stomach to make…. 

More surface area resulting in absorption & digestion

How do extra folds help the digestive process?

Duodenum

Short, relatively smooth inside (short villi, few plicae). Evolved to receive the contents of the stomach.​

Jejunum

Many deep plicae, lots of very long villi. Evolved to maximize absorption and digestion at the border.​

ileum

Few plicae, short villi. Evolved to absorb “the rest” of what the jejunum did not. Longest region.​

Gastrin

secreted in pyloric region and stimulated by presence of proteins it the stomach, increase stomach mobility and enzyme production.

Secretin 

released by duodenum when chyme is present. Decrease gastric mobility.

GIP

 released when fat and carbs are present. Inhibit gastric activity. Also, insulin is released. 

CCK

 released when chyme arrives to the duodenum, for lipids. Ejects bile into the duodenum.

VIP

hormone that regional capillaries dilate to absorb more. 

Cephalic Phase

when you see/smell/taste food, there is an increase of gastric juice production

Gastric Phase

When food arrives in stomach, the stomach extends, PH lowers, & gastrin is secreted (3-4 hours long)

Intestinal Phase 

phase with chyme in duodenum, enterogastric reflex- gastrin production inhibited, motility lowered, and mucus production increased in duodenum

Gastric Central Reflexes

when stomach is fully extended, food is moved faster into the duodenum. 

Large Intenstine

1.5 m long, reabsorb water and compact contents. Store fecal material, and absorb vitamins.  Lack Villi, have intestinal glands (mucus) and no enzymes. Lubricate due to dryer material moving through. (cecum, colon, rectum)

Cecum

expanded pouch, compaction. Ileocecal valve- cecum, ileum connection.  Appendix attaches here, which is lymphoid nodule.

Colon

4 sections: ascending, transverse, descending, and sigmoid. Large diameter/thin walls.

Rectum

expandable, movement into rectum triggers urge to defecate. Internal sphincter (smooth/involuntary) and external sphincter (skeletal/voluntary)

Salivary glands

 in mouth, saliva production (99.4%) water. And antibodies, buffers, and lysozymes and amylases. Flushes oral surfaces. Keeps pH at 7. 

Liver

 synthesizes and secretes bile.  4 lobes- right and left and quadrate and caudate lobe. Bile- contains bile salts that break down lipids into small droplets. Also has toxins from liver. 

Gall bladder

 stores bile. When the hepatopancreatic sphincter (valve into duodenum) opens, bile emptied into the duodenum

bile will continuously dump into duodenum and be recycled by the small intestine back to the liver

What happens if there is no gallbladder? 

Pancreas

secretes biocarbonate that neutralizes stomach acids) and enzymes for all types of nutrients.

 Pancreatic alpha-amylase

breaks down carbs

Pancreatic lipase

breaks down lipids

Nucleases

breakdown RNA & DNA

Proteolytic enzymes

breaks down proteins

1. Adjust blood volume/ pressure

2. Regulate blood plasma/ concentration of na, k, cl, & other ions

3. Regulate Ph, conserve nutrients & remove toxins

What are the functions of the urinary system?