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What are the major subdivisions of the digestive system?
- oral cavity
- small and large intestines
- cloaca/ anus
Accessory organs of the digestive system
- oral glands
- gall bladder
means "common sewer"
exit-- solid waste, liquid, gametes
What are adaptations?
differences you see are correlated with the type of food you eat and the abundance of food that is available they both play a role in the anatomy of the digestive tract
Examples of adaptations?
hummingbirds have a different tract from carnivores because their food is readily absorbed, whereas meat is not
Mouth and oral cavity: Oral Cavity
oral cavity begins at the mouth and ends at the pharynx
- - fish have a very short oral cavity
- - tetrapods typically have a longer one
- --> The mammalian mouth is specialized for suckling in addition to mastication (physical breakdown of food)
Mouth and oral cavity: Palate
Palate forms the roof of the mouth
- primary palate: leads into the oral cavity through internal nares
- Those that have a secondary palate: the nasal passages are actually above the secondary palate and open at the end of the oral cavity
Mouth and oral cavity: Teeth
- Teeth are unique among vertebrates
- Come from dermal armor
There are toothless vertebrates in every class
What is the toothless class?
living birds are probably the only class that do not have teeth (edentate); they use their beaks and bills to physically break the food
- - captures the food
- - helps in gathering food
- - tastes via taste buds
- - helps to manipulate to prepare it for swallowing
- - helps create a solid mass called the bolus, which helps in swallowing
- - thermoregulation in some vertebrates
- - grooming
- - speech in humans
Explain tongue in carnivores.
- In carnivores, the surface of the tongue is roughened, almost like the feel of a file
- - they are really keratinized spiny projections from the surface of the tongue
- - allows for the tongue to grab onto and rasp the food--papillas
Some tetrapods do what?
Use their tongues for lingual feeding, actually projecting their tongue at prey. The surface of the tongue is sticky and when the prey get on the tongue--adheres-- the tongue retracts with the prey on it
ex: salamanders and lizards
Tongue mobility (1)
- turtles, crocodiles, some birds, and whales have pretty much an immobile tongue
- - it is just a muscular organ that adheres to the floor of the mouth; cannot be extended
Tongue mobility (2)
Snakes, some lizards, amphibians, and some birds have tongues that are really long and can move in and out of the oral cavity
Tongue mobility (3)
- Mammals have a tongue attached to the floor of the oral cavity through a mucosal piece called the fremula (piece of flesh that anchors the tongue to the ground)
- - even though it is attached, it can still be extended a short distance
in aquatic organisms, there is no need for watery glands because they have a watery medium; water glands are few or none and are really a terrestrial phenomenon. The function is to bind and shape the food--> saliva
In most vertebrates, the glands also secrete an enzyme called salivary amylase (ptyalin)
short muscular tube used for transport of air and food
- exception: in fish, it is also used for respiration
- in tetrapods, it is part of the foregut
Explain the end of the pharynx.
At the end of the pharynx, there is a split at the entrance of the larynx.
The entrance into the larynx is a slit called the glottis. If it is food, it goes into the esophagus; if it is air, it goes into the trachea
Explain the pharynx in mammals.
In mammals, there is a cartilage called the epiglottis as part of the glottis, positioned over the slit and extends over the glottis. It really ensures food to go down here.
When you're eating, the epiglottis lifts up and covers the glottis, preventing food from getting into the trachea