Phylum Chordata and Perch Anatomy

Phylum Chordata

• Organisms in this phylum possess a dorsal, hollow nerve cord that becomes the brain and spinal cord in mammals
• A notochord is present, which is a cartilaginous rod that develops dorsal to the primitive gut in the early embryo
• Lower chordates retain the notochord throughout life
• In vertebrates, the notochord is surrounded and persists as the soft center of the intervertebral discs
• Paired pharyngeal pouches are present in the pharynx or throat during some life stage
• Aquatic chordates' pharyngeal pouches perforate to form pharyngeal gill slits
• Higher chordates' pharyngeal pouches are present only during embryonic development
• There is a gland or tissue which concentrates iodine
• A post-anal tail extends past the anus
• Phylum Chordata is divided into three subphyla, including Subphylum Vertebrata
• The perch (class Osteichthyes) and the rat (class Mammalia) are of interest in this lab

External Anatomy of the Perch (Perca flavescens)

• Bony fishes are the most numerous vertebrates, occupying marine and freshwater environments
• The perch is an aquatic vertebrate
• The perch has a fusiform body shape, flattened laterally and streamlined to minimize resistance in the water
• Overlapping scales cover the body
• Overlapping scales minimize resistance to movement
• A mucous layer protects the scales
• Modern fish scales are remnants of bony armor from ancient vertebrates
• The anus is the larger, more anterior opening on the ventral surface
• The urogenital opening is the smaller, more posterior opening on the ventral surface
• Each lateral surface has a crescent-shaped opening to the gill chamber
• A bony operculum covers each gill chamber
• Four gill arches with attached gills are found by bending the operculum backward
• The lateral line system is a pigmented line extending from the operculum to the tail
• The lateral line system contains sensory pits and detects low-frequency vibrations
• The perch's body consists of the head, trunk, and tail

Perch Head

• The terminal mouth is at the anterior tip
• The mouth position reflects feeding habits
• The perch overtakes prey while swimming
• The mouth contains many sharp uniform teeth
• There are four nasal apertures (nares) just above the mouth
• Anterior nasal apertures connect to form the posterior nasal apertures
• The nares are not connected to the mouth
• The large eyes lack eyelids
• The large eyes are covered by transparent integument

Perch Trunk and Tail

• The paired fins are homologous to tetrapod appendages
• Pectoral fins are located just posterior to the opercula and attach to the pectoral girdle
• Pelvic fins are posterior and ventral to the pectoral fins
• The tail tapers from the trunk and ends as a laterally compressed paddle as the symmetrical caudal fin, and is correlated with the presence of a swim bladder

Perch Median Fins

• Four median unpaired fins exist
• Caudal fin
• Anal fin is posterior to the anus
• Anterior dorsal fin at the trunk's anterior end
• Posterior dorsal fin is posterior to the anterior dorsal fin

Perch Muscular System

• Muscles enable movement, eating, and reproduction
• Vertebrate skeletal muscles include axial and appendicular muscles
• Axial muscles are along the body's longitudinal axis
• Appendicular muscles are in the limbs and girdles
• Other muscles are associated with the eyes, jaws, gills, and opercula
• Perch musculature is less complex than that of tetrapods
• Most perch muscles are axial muscles
• Perch muscle mass is about twice that of most tetrapods based on body size
• The perch moves via lateral undulations from axial muscle contractions
• Contractions are inefficient, requiring a larger muscle mass for locomotion

Perch Muscular system Dissection

• Remove a 2-3 cm strip of skin midway between the pelvic and anal fins on the left side
• The strip extends from the anterior dorsal fin to the mid-ventral line
• Exercise care when removing the skin

Perch Myomeres & Myosepta

• Axial musculature is composed of myomeres
• Myosepta, bands of connective tissue, separate myomeres
• Each myomere is zig-zag shaped like a tilted "W"
• A horizontal septum divides the myomeres into dorsal and ventral portions
• The musculature's primary function is to support body viscera
• Appendicular muscles are small and simple due to paired fins increasing stability
• The perch musculature associates with the jaws, gills, opercula, and skull
• This head musculature is complex due to many moveable bones in the perch skull
• Head musculature functions: feeding and respiration

Perch Digestive System

• The gastrointestinal (GI) tract is a tube starting at the mouth and ending either into a cloaca or via an anus
• Functions: ingestion, digestion, absorption, and waste elimination
• The GI tract is subdivided into oral cavity (mouth), pharynx (throat), esophagus, stomach, small intestine, and large intestine
• Accessory organs include teeth, tongue, salivary glands, liver, and gallbladder
• Digestive organs are located in the coelom, suspended by a mesentery extending from the median dorsal wall
• Blood vessels and nerves extend to organs via the mesentery
• The digestive tract lumen is continuous with the external environment
• Digestion results in small molecules such as monosaccharides, glycerol, fatty acids, and amino acids
• Products diffuse across epithelial cells lining the GI tract to enter the bloodstream and tissue fluid
• Breakdown products are taken into the internal environment for further processing

Digestive Tract Anatomy

• Differences in anatomy correlate primarily with the nature and abundance of food
• Plant cell walls are indigestible by animal enzymes
• Plant matter requires longer processing in the digestive system
• Herbivore intestines are longer than those of omnivores and carnivores
• Herbivores rely on bacteria and protozoa to break down cellulose
• A caecum is a large blind sac or tube at the junction of the small and large intestines where food is processed by microorganisms
• Caeca increase surface area and are found in the digestive tracts of animals

Fish vs Mammal Mouths

• In fish, the mouth opens into the oropharyngeal cavity, which extends to the esophagus
• Fish take in both respiratory water and food through the mouth
• Fish have a primary tongue, an immoveable elevation on the floor of the oropharynx
• Fish have no salivary glands
• Carnivorous fish utilize teeth to capture and hold prey to swallow
• In mammals, the mouth opens into the oral cavity, which extends to the pharynx
• The palate separates the respiratory and oral cavities, allowing simultaneous breathing and food processing
• Salivary glands exist in all mammals
• Tongue is protrusive
• Saliva functions as a lubricant and may contain enzymes to break down carbohydrates

Mammal Teeth

• All mammals except baleen whales and anteaters have teeth
• A mammal's teeth types reflect its diet
• Molars have flat surfaces for crushing and milling, and are characteristic of herbivores
• Premolars shear, cut, and slice, except in advanced herbivores
• Incisors are chisel-shaped teeth useful for biting and are found in herbivores, carnivores and omnivores
• Pointed canine teeth tear flesh and are useful for catching and holding prey

Perch Digestive System Specifics

• Includes the gut tube, liver, and pancreas
• To perform a Dissection, hold the fish with the ventral side up
• Insert scissors in front of the anus, cut up the midline to between the opercula, then cut around the gill chamber to the top of the body cavity, another incision from the starting point
• Remove the lateral body wall to expose the body organs

Internal Perch Organs

• Esophagus: Short, straight tube from mouth to the stomach, located at the extreme anterior end of the body cavity
• Stomach: Larger, thick-walled U-shaped tube where mechanical and chemical breakdown begins
• Stomach size depends on how much much food it contains
• Pyloric Caeca: Three blind-ended tubes, extending from the gut at the junction of stomach and intestine, that serve secretory and absorptive functions
• Intestine: S-shaped loop, originating from the stomach, and extending directly to the anus, in which the length correlates to animal's lifestyle (e.g. herbivores vs. carnivores)
• Liver: Located just anterior to the stomach, drains bile from liver, and opens into the intestine, necessary for proper digestion of fats
• Pancreas: A digestive gland along the ventral border of the intestine, which secretes digestive enzymes into the intestine and hormones into the blood
• Spleen: Football shaped organ lying on the posterior dorsal surface of the stomach that functions in production and maintenance of blood cells

Perch Excretory System

• Kidneys eliminate nitrogenous wastes and conserve materials
• Maintain internal environment
• Perch urinary system: kidneys, which are dorsal to the swim bladder
• Two small ducts unite to form one common ureter
• The common urogenital opening empties the ureter and the gonoduct, which passes genital products from the gonad to the exterior
• The urinary bladder is a small sac at the most posterior, ventral end of the body cavity
• A separate structure in the male, incorporated into the oviducts in the female to form the urogenital sinus
• Kidneys and swim bladder are visible structures in a dissected specimen

Perch Reproductive System

• Only one sex is seen during a dissection, though one is responsible for knowing both
• Male: Testes are white elongated bodies below the air bladder joined by mesentery and sperm pass through the urogenital opening
• Examine a dissected male perch
• Female: Ovary containing epithelial sac filled with eggs, between intestine and air bladder eggs pass through urogenital opening. The ovaries are paired but fuse into one

Perch Respiratory System

• The dissected specimen will have the right operculum removed to expose the gills
• The gills attach to each of the four pairs of branchial arches on the anterior surface of arches are gill rakers
• Each gill has two sets of filaments, one extending anteriorly, and the other posteriorly known as holobranchs with small lined folds called lamellae
• Gill capillaries exchange oxygen and carbon dioxide between water and blood
• Water enters the mouth and the pharynx with closed opercula as oral cavity contracts and water is forced through the gills
• Water passes over the gill filaments facilitating exchange of oxygen and carbon dioxide
• A counter-current system maximizes the movement of oxygen into the blood
• Gills performs excretory functions by excreting nitrogenous wastes and marine fish excete salt

Perch Circulatory System

• Transports Oxygen, food, carbon dioxide, and waste
• Consists of the heart, arteries, veins, capillaries, and blood
• Arteries carry blood away from the heart and veins carry blood from capillaries back to the heart
• It is a typical low pressure single type system in which the heart is a single pump and there is a single circuit of blood flow
• Venous(deoxygenated) blood from the body is pumped to the gills to oxygenate blood
• Blood makes a single circuit during circulation and returns to the heart before being pumped

Perch Heart

• A pericardial cavity is exposed by extending the ventral incision and the pericardial membrane is freed
• A heavy membrane is the transverse septum separates the anatomical cavities
• The fish heart consists of four parts: a sinus venosus, and atrium, ventricle, and bulbus arteriosus
• These parts arrange to produce an S-shaped organ
• The sinus venosus receives blood from cardinal veins and hepatic sinus, opening directly into the Atrium
• The atrium is equivalent to paired atria of vertebrates, thicker walled and larger then the sinus venosus
• The ventricle is a structure, like the atrium, with a single chamber where contraction is prevented by the valve
• The Bulbus Arteriosus is the portion of the perch and is an enlarged portion of the ventral aorta, and is the vessel where blood flows

Rat Anatomy (Rattus rattus)

• Orders of Mammals are recognized by differentiated appearance such as a rat
• Mammals have 2 characteristics
  • Have hair at the time of development
  • Female Mammals possess mammary glands
• The major characteristitsc are from a white rat an albino and a rodent that are numerous
• Rodents are terrestrial such as squirrels, mice, guinea pigs, porcupines, and beavers.

General Features of a Rat

• Finding external features with dissection
• A Rat is a tetrapod with digitigrade locomotion only in the Elevated digits
• The body covering is hair, derived from the skin, and tail scales, also from epidermal region
• Divided into four areas, Head, Neck, Trunk, and Tail

Rat - Head & Neck

• The head is separated by a moveable neck
• The mouth bounded by developed upper/lower lips
• Upper lip is cleft
• Visibility of, Incisor teeth,
• The external nares are on flexible nose with protected eyes
• Ears posses a pinna and external auditory. There is a tympanic membrane.

Rat - Head Continued

• Possess special sensory, vibrissae out from the snout, eyelid, cheek and chin
• Trunk divided with an interior and posterior
• Abdomen contains ribs and the thorax doesn't.
• Teats and nipples on the trunk with 12 distributes between the abdomin and thorasic region

Rat - Urogenital/Anal openings & Tail

• Females have separate urogenital openings, anterior and vaginal orifice
• The anus is at the base, posterior to the orifice
• In males, the urethra is common
• There is a scrotum at the base of the tail containing testes
• The tail is scattered in hair

Rat - Muscular System

• The muscular system changed over evolution with muscular support
• Axial musculature is lost and dorsal supports the head/column
• The ventral supports layers
• Ventral muscles perform over the appendages
• Skin is removed and muscles are to be located
  • external oblique layers on the abdomen
  • internal oblique layers and fibers
  • Transverse oblique the third layer
  • Rectus abdiminous runs laterally
  • Latissimus Dorsi runs along left arm

Rat - Appendicular Muscles

• There are biceps brachhii with oppose fucntions
• Two muscles act as Antagonist

Rat - Digestive System

• Salivary identifies the gland and is not deep cut
• There are gland pairs
• Parotid gland is beneath the ear, ventrolateral
• Submaxillary glands lies ventral and larger
• Sublingual glands overlying submaxillary glands
• Extraorbital gland a fourth gland for tears
• Oral: cutting the mandible and jaw
  • locate structure and dental system
  • incisors/molars are the bony root, separating cavities. With growth

Rat - Abdominal Cavity

• Following incision lines, is opposing scalpel used to avoid damage, sternum incision
• Incision through abdominal toward snip, penis and thoracic
• Make thoracic/abdominal cavities with running water
• The coelom lies with organs, internal stomach/instetines
• Abdominal cavity covered in mesothelium and formed from the following membranes
• Propermesentery extending wall to inside
• Falciform extending from ventral liver/diaphram
• The Parietal peritoneum, is the shiny lining membrane

Rat - Peritoneum

• visereal organs
• Greater and lateral omentum joining

Rat -Digestion

• Has a stomach for storage
• A cardiac to entrance esophagus
• fundic middle area opening to doudenum, and to point pyloric, The stomach contains folds walls
• Small intestine is a 3 region that is anteriror,mid jeunum, posterior as the iluem
• Bile from pancreas and liver, intestine walls
• The large intestine The lleum that consist 4 and a caecum for microorganisms, a transport and descension
  • The Liver where duedenun connects produced
  • The Panacreas contains hormones

Rat - Osmoregulatory Systerm

• Kidneys are located on on the body walls within
• The vertor exits from vessels and kidneys with Hilus
• urinary bladder with storage
• Uretha exites, the urinary from exterior
• Females has pig system
• Testes outer and medula and the cortexes