Lymph-interstitial fluid

Lacteals-carry fatty nutrients to blood

Lymph nodes-screen out foreign

matter/pathogens from lymph

Absent in fish,urodele amphibians

Thought to be absent in birds.

Anurans have proto-lymph nodes.

Thymus Gland- T lymphocytes become immunocompetent. Shrinks with the age of the animal. Prominent in all vertebrates. Not found in agnathans.

Developed from pharyngeal pouches in reptiles

Second pharyngeal pouch in anurans

Behind eye in fish

Ventral surface of upper chest cavity in most mammals & birds.

largest lymph organ,

proliferates lymphocytes,

filters blood,

extracts aged and defective blood cells & platelets, stores breakdown products.

Not found in agnathans

Tonsils-has blind passages called crypts that trap bacteria and draw them into the tonsils. Critical in developing immune "memory"

Between 2 and 6 paired or unpaired.

(Humans have 2 pairs, one unpaired

Peyer's patches in the intestines

Bursa of Fabricius in birds

Lymphomyeloid organs in branchials of larval amphibians

Bone marrow-red blood cell production in terrestrial vertebrates, reduced in lungless salamanders

Renal Lymphnoid-in fishes

Chapter 13 The digestive system

Overview of feeding-

A tube within a tube

Function: absorption of food into the body and elimination of undigestible components of food.

Digestive begins at the mouth and ends at the anus

Mouth

Buccal (oral) cavity (oropharyngeal cavity in fishes)

Teeth

Tongue

Oral Glands (salivary)

Pharynx

Esophagus

Stomach

Pancreas

Gall Bladder

Liver

Small intestines

Duodenum

Jejuneum

Ileum

Cecum

Large intestines

Cloaca (or rectum)

Anus

Mouth

Size limits the size of prey

Flexibility, big mouths, or specialized jaw attachments may allow some animals to eat prey bigger than their head-or even body.

Gape limited in birds and reptiles

Deep sea angler's

Lizards

Snakes

Mammals have a sphincter muscle that allows a tight seal to form around the mouth.

Lips are common to mammals-have cheeks that may store and hold food to chew later. Lips used for suckling among offspring. Accessory communication organ in many mammals

Oropharyngeal cavity in fish is defined as a cavity directly behind the mouth that contains teeth and is perforated by gill slits. Terminates in a short esophagus

The buccal cavity or oral cavity houses a tongue, teeth, but no gill slits and contains a palate. This cavity ends at the pharynx or esophagus.

The roof of the mouth is an important consideration in both feeding and respiration.

Primary palate-bony structure covered with epithelium, composed of palatine bone and other bones (vomers, pterygoids, parasphenoids, sphenoids etc.)

Secondary palate-paired lateral bones that meet at the midline of the roof of the mouth (premaxilla and maxilla bones-and palatines and pterygoids in some species).

Hard palate-anterior part of the secondary palate

Soft palate-found in mammals, fleshy posterior portion of secondary palate

Most fishes have a primary palate that is bony and lacks any internal nares.

Amphibians and lungfish have this palate perforated anteriorly with internal nares that enter into the mouth.

This means that lungfishes and most amphibians can't ventilate their respiratory system the same time they are feeding. This is true of fishes as well since it disrupts their dual pump ventilation mechanism.

This translates into animals that swallow their food whole so that they can breath quickly after prey capture.

Birds and most reptiles have an incomplete secondary palate that leaves a broad gap in the roof of the mouth. This somewhat limits chewing or mastication of food. On the plus side, this means many reptiles can discretely pick their nose with their tongue without having it leave their mouth.

Crocodiles and mammals have a complete secondary palate that allows for longer periods of either chewing prey or holding prey until it is dead.

How then do snakes breath while trying to eat a large prey item if they don't have internal nares that pass posterior in the buccal cavity?

Snakes move their trachea around their food instead.

During prey consumption, the trachea is pulled to a ventral and anterior position and pops out in the front of the buccal cavity as a "snorkel" for breathing.

Teeth derived from bony dermal armor that extended into the oropharyngeal cavity

Acrodont -outer surface or summit of jaw (teleost fishes)

Pleurodont-inner surface of jaw.

Thecodont -occupy bone sockets

Polyphyodont dentition-is replaced indefinite number of times over the lifetime of the animal (crocodiles may replace the front tooth 50 times during its life).

Diphyodont dentition-has two replacements (found in most mammals).

Monophyodont

Tooth Structure

Enamel -grinding or cutting surface

Dentin-below enamel

Cementum-base of roots

Pulp center

Pattern of cusps and layering of enamel and dentin determine tooth types:

Examples

Lophodont-ridges of enamel that connect cusps across the occlusal surface

Bunodont-convex broad cusps along occlusal surface

Selenodont-concentric rings of enamel ridges connecting cusps

Teeth Types

Incisors

Canines

Premolars

Molars

removing flesh (lampreys & carnivores)

Increases swallowing efficiency

Essential for taste bud function

Maintains buccal cavity moisture

Mucous decreases evaporation

Agglutinate food

Enhances chewing

Increases swallowing efficiency

Reduces choking hazard

Envenomate prey -digest prey from within

Toxins for predator defense

"Glues" prey to buccal cavity

Feed young (goblet cells of catfishes)

lampreys)

Pharynx-corridor for food and air (stops at beginning of trachea and esophagus)

Derivatives of the pharyngeal pouches during development:

Middle and inner ear (eustachian tube) (1^st pouch)

Palatine tonsils (2^nd pouch)

Parathyroid gland (3^rd & 4^th pouch)

Thyroid or anatomical equivalents (5^th pouch)

Three seals:

1. Lips
2. Soft palate and tongue
3. Soft palate and epiglottis

Third type not present in humans. Lengthened pharynx precludes this seal-makes choking more common, but aids in vowel formation and differentiation during speech.