Chemical senses Web Quest Digestive system begin lecture HW: parts of dissection mini-packet

(whatever is not completed in class)

Digestion› Breakdown of ingested food› Absorption of nutrients into the

blood Metabolism

› Production of cellular energy (ATP)

› Building and breaking down cellular activities

Two main groups› Alimentary canal – continuous coiled

hollow tube In adults, the alimentary canal is about 30 feet long.

Other names for the alimentary canal include the gastrointestinal (GI) tract, digestive tract, alimentary tract

› Accessory digestive organs

Figure 14.1

Mouth Pharynx Esophagus Stomach Small intestine Large intestine Anus

Lips – protect the anterior opening

Cheeks – form the lateral walls› Keep food in mouth

Hard palate – forms the anterior roof

Soft palate – forms the posterior roof› Keeps food out of nasal passage

Uvula – fleshy projection of the soft palate. Helps you not to choke on food

Figure 14.2a

Vestibule – space between lips externally and teeth and gums internally

Oral cavity – area contained by the teeth

Tongue – strong muscle which mixes & moves food in the correct direction

Figure 14.2a

Mastication (chewing) of food Mixing masticated food with saliva Initiation of swallowing by the

tongue Allowing for the sense of taste

Figure 14.2a

Serves as a passageway for air and food

Food is propelled to the esophagus by two muscle layers

Food movement is by alternating contractions of the muscle layers (peristalsis)

Runs from pharynx to stomach through the diaphragm

Conducts food by peristalsis (slow rhythmic squeezing)

Passageway for food only (respiratory system branches off after the pharynx)

Located on the left side of the abdominal cavity

Food enters at the cardioesophageal sphincter

Food empties into the small intestine at the pyloric sphincter

Rugae – internal folds of the mucosa

Acts as a storage tank for food Churns food into a paste called

chyme. Chemical breakdown of protein

begins

Simple columnar epithelium› Mucous neck cells – produce a sticky

alkaline mucus› Gastric glands – secrete gastric juice› Chief cells – produce protein-

digesting enzymes (pepsinogens)› Parietal cells – produce hydrochloric

acid› Endocrine cells – produce gastrin

Gastric pits formed by folded mucosa

Glands and specialized cells are in the gastric gland region

The body’s major digestive organ

Site of nutrient absorption into the blood

Suspended from the posterior abdominal wall by the mesentery (connective tissue sheet)

Duodenum› Attached to the stomach› Curves around the head of the

pancreas Don’t worry about the other 2

Bile enters from the gall bladder- breaks down lipids

Fingerlike structures

Give the small intestine more surface area-pull out more nutrients from food.

Figure 14.7a

Small projections of the plasma membrane

Found on absorptive cells

Figure 14.7c

Absorptive cells Blood capillaries

Figure 14.7b

Larger in diameter, but shorter than the small intestine

Frames the internal abdomen

Figure 14.8

Absorption of water Eliminates indigestible food from the

body as feces Does not participate in digestion of

food Goblet cells produce mucus to act as

a lubricant

Appendix› Accumulation of lymphatic tissue

that sometimes becomes inflamed (appendicitis)

Colon› Ascending› Transverse› Descending› S-shaped sigmoidal

Rectum Anus – external body opening

In class complete the following in the mini-packet› NOTE: YOU WILL BE JUMPING AROUND!

The human digestive tract pg 175 › DO NOT DO pg 176

Stomach and small intestine: both sides If you do not finish this it will become

homework If you have time color Overview of the

System- it is not required BUT if you do a nice job and complete the entire thing in colored pencil or crayon you can earn EC

Put packet into bin. You’ll get it back today for your HW

Finish digestion lecture (quick!) Final Dissection- digestive system HW: finish digestion mini-packet

Salivary glands Teeth Pancreas Liver Gall bladder

Saliva-producing glands› Parotid glands – located anterior to

ears Mixture of mucus and serous fluids Helps to form a food bolus Contains salivary amylase to begin

starch digestion Dissolves chemicals so they can be

tasted

The role is to masticate (chew) food Humans have two sets of teeth

› Deciduous (baby or milk) teeth› 20 teeth are fully formed by age

two

Permanent teeth› Replace deciduous teeth beginning

between the ages of 6 to 12› A full set is 32 teeth, but some

people do not have wisdom teeth

Incisors Canines Premolars Molars

Crown – exposed part› Outer enamel› Dentin› Pulp cavity

Neck› Region in contact

with the gum› Connects crown to

rootFigure 14.10

Root› Periodontal

membrane attached to the bone

› Root canal carrying blood vessels and nerves

Figure 14.10

Produces a wide spectrum of digestive enzymes that break down all categories of food

Enzymes are secreted into the duodenum

Alkaline fluid introduced with enzymes neutralizes acidic chyme

Largest gland in the body Located on the right side of the body

under the diaphragm Connected to the gall bladder via the

common hepatic duct Produces bile which breaks down

fats

Sac found in hollow of liver Stores bile from the liver & releases

in the presence of fatty food Gallstones can cause blockages and

PAIN

Ingestion – getting food into the mouth

Propulsion – moving foods from one region of the digestive system to another

Food must first be well mixed Rippling peristalsis occurs in the

lower stomach

Figure 14.15

The pylorus meters out chyme into the small intestine (30 ml at a time)

The stomach empties in four to six hours

Figure 14.15

Peristalsis – alternating waves of contraction down esophagus, large intestine

Segmentation – moving materials back and forth to aid in mixing, small intestine

Sluggish peristalsis Mass movements

› Slow, powerful movements› Occur three to four times per day

Presence of feces in the rectum causes a defecation reflex› Internal anal sphincter is relaxed› Defecation occurs with relaxation of the

voluntary (external) anal sphincter

Mechanical digestion› Mixing of food in the mouth by the

tongue› Churning of food in the stomach› Segmentation in the small

intestine

Chemical Digestion› Enzymes break down food molecules

into their building blocks› Each major food group uses different

enzymes Carbohydrates are broken to simple sugars

Proteins are broken to amino acids Fats are broken to fatty acids and alcohols

Absorption (diffusion of macromolecules)› End products of digestion are

absorbed in the blood Defecation

› Elimination of indigestible substances as feces

Figure 14.11

Digestive system & associated organs Check out the kidneys Check out reproductive if there is time Thank your pig, place you pig in the bag

and then in the garbage.

HW: finish mini-packet Thursday: pizza lab! FYI Juniors: you take your final with

seniors which is next week.