ANSWERS TO OBJECTIVES FOR BIO 3220 QUIZ 4

A. MUSCULAR SYSTEM

1. Explain the overall function of muscles.
Muscles function in locomotion, posture, protection, and heat production.

2. Classify muscle tissue according to microscopic appearances and nervous control.
Skeletal muscle appears striated, or striped, and cylindrical with the nuclei peripheral. Skeletal muscle cannot contract without stimulation from a motor neuron. Cardiac muscle appears striated, cylindrical and branched, with the nuclei central, with intercalated discs. Its movement is involuntary. Smooth muscle appears smooth, spindle-shaped with the nucleus central. Its movement is involuntary and is controlled by the autonomic nervous system.

3. Describe the parts of a muscle cell (fiber), including myofibril, myofilament, actin, myosin, and sarcomere.
Each muscle fiber contains an array of myofibrils that are stacked lengthwise and run the entire length of the fiber, mitochondria, an extensive endoplasmic reticulum, many nuclei. Each myofibril is made up of arrays of parallel filaments. The thick filaments have a diameter of about 15 nm. They are composed of the protein myosin. The thin filaments have a diameter of about 5 nm. They are composed chiefly of the protein actin along with smaller amounts of two other proteins, troponin and tropomyosin. The myofibrils have distinct, repeating microanatomical units, termed sarcomeres, which represent the basic contractile units. The sarcomere is defined as the region of myofilament structures between two Z-lines. Shortening of the sarcomeres in a myofibril produces the shortening of the myofibril and, in turn, of the muscle fiber of which it is a part.

4. Define motor neuron and motor unit.
Motor neuron – a neuron that stimulates muscle contraction
Motor unit – the motor neuron plus the number of myofibers it innervates

5. Define intercalated disc.
Intercalated disc are regions where adjacent cardiocytes interlock and where gap junctions permit electrical coupling between the cells.

6. Define and give an example of a somatic muscle.
Somatic muscles consist of all skeletal muscle except branchiomeric muscle. It is voluntary muscle and is found in the body wall and appendages.

7. Define and give an example of a visceral muscle.
Visceral muscle is found in various parts of the body such as the arteries, the bladder, the digestive tract as well as in many other organs. Visceral muscle is smooth muscle as it doesn't have cross striations. Visceral muscle contracts slower than skeletal muscle but the contraction can be sustained over a longer period of time.

8. Compare and contrast red and white muscle fibers.
Red – more blood supply; aerobic metabolism; has myoglobin – red pigmented protein that stores oxygen; fatigue resistant; ex. fish swimming long distances, posture of tetrapods
White – not as much blood supply; anaerobic metabolism; fatiguable; fish spurts of swimming, tetrapod sprints

9. Describe the following gross anatomical features:
Origin – the relatively fixed attachment to skeleton
Insertion – the muscle attachment point that is relatively free to move
Fascia – a loose connective tissue that binds muscle to muscle and skin to muscle
Tendon – join muscle to bone; cord-like
Aponeurosis – a tough flat sheet of connective tissue serving to distribute the tension of a muscle; sheet-like tendon

10. Characterize the various muscle shapes.
Strap – fleshy, wide attachments at each end; ex. sternocleidomastoid
Teardrop – teardrop shaped muscle; ex. pectorals
Spindle – cigar-like shape with pinched ends; ex. extremities
Heads – multiple origins; ex. forearm of cat
Sheets – fiber strands lie in flat bundles; ex. abdominals
Fan – fan shaped muscle converging towards attachment point; ex. trapezius
Circular/sphincter – circular-shaped muscles; ex. sphincter muscles
Pinnate – breathing muscle unique to mammals; ex. diaphragm

11. Review the following muscle actions:
Flex – reduce angle between adjacent bones
Extend – increase the angle
Adduct – move parts inward toward midline
Abduct – move parts outward
Levator – raise parts
Depressor – lower parts
Protract – push part away from its base - forward movement
Retract – draw it back
Sphincters – constrict openings
Constrict – compress spaces
Dilator – oppose both of above
Rotator – turning
Supinator – rotators that turn palms of hands upward
Pronator – turn them downward
Tensor – pulling tight/taut

12. Contrast agonist, synergist, and antagonist.
Agonist is the primary mover. Synergist is muscle that supplements/helps movement. Antagonist is muscle that opposes movement.

13. Discuss the embryologic development of muscle. How is phylogeny of muscles studied?
The mesoderm gives rise to the epimere, mesomere, and hypomere. The epimere gives rise to the dermotome which becomes some smooth muscle, the sclerotome, and the myotome which becomes most muscles except for branchiomeric muscle. The hypomere gives rise to somatic muscles, muscles of the body wall, and splanchnic muscles, smooth muscle of the gut and cardiac muscle. Embryology and nerve supply are also used to study the phylogeny of muscles. Embryology helps to provide for major muscle categories. The nerve supply has been shown to be the most consistent indicator of homology.

14. Define metamerism, somite, and myoseptum.
Metamerism – The condition of having the body divided into metameres (somites), exhibited in most animals only in the early embryonic stages of development
Somite – segmental mass of mesoderm in the vertebrate embryo, occurring in pairs along the notochord and developing into muscles and vertebrae; also called metamere
Myoseptum – the septum or divider between adjacent myotomes which are segments of a somite in a vertebrate embryo that differentiates into skeletal muscle

15. Distinguish axial from appendicular muscles.
The axial musculature begins are myotomes separated by myosepta. The axial muscles are then further divided into two regions, muscles on the dorsal part of the body (epaxial muscles) and mucles on the muscles on the ventral part of the body (hypaxial muscles). These regions are separated by the lateral or horizontal septum. The axial musculature associated with the trunk can function either in locomotion or breathing. They include the muscles of the trunk and tail, hypobranchial, tongue, and extrinsic eye muscles. Appendicular muscle development originates from the somites as outgrowths of the somite myotome into the limb bud. Such outgrowths are called the myotomic buds to the appendages. As the limb buds grow, the appendicular musculature subdivides into the muscle mass that lies above the appendicular skeleton (dorsal muscles) and the mass that lies below the appendicular skeleton (ventral muscles).

16. Characterize epaxial muscles. Discuss their function and innervation. (See Muscle Handout.)
Epaxial muscle is the region of axial muscle on the dorsal part of the body. It functions to extend or straighten the spine (dorsoflex) and provides some lateral flexion. It is innervated by the dorsal rami of spinal nerves.

17. Characterize hypaxial muscles. Discuss their function and innervation.
Hypaxial muscle is the region of axial muscle on the ventral part of the body. It functions to bend the spine (ventroflex) and provides some lateral bending. It is innervated by the ventral rami of spinal nerves.

18. Characterize hypobranchial muscles. Discuss their function and innervation.
Hypobranchial muscle is located below the pharynx, from the pectoral girdle to the jaw. It functions in respiration and feeding. It is innervated by 12th cranial nerve and ventral rami of cervical nerves.

19. Characterize extrinsic eye muscles. Discuss their function and innervation.
Extrinsic eye muscles are formed from epaxial parts of 3 pairs of head myotomes. They function as a pattern of muscles that move the eye. They are innervated by the 3rd, 4th, and 6th cranial nerves.

20. Describe the axial muscles of agnathans, fish, and tetrapods, including a description of the following muscles: dorsalis trunci, intervertebrals, longissimus, spinales, iliocostalis, subvertebrals, abdominal obliques, transverses, intercostals, rectus abdominus, and diaphragm.
Agnathans – lateral septum lacking; segmentation present; axial skeleton virtually absent; no hypobranchial musculature; branchial muscles not prominent; extrinsic eye muscles develop from head myotomes (but hard to homologize with other vertebrates)
Jawed fishes – lateral septum divides epaxial and hypaxial portions; myomeres are more angled than in cyclostomes (dorsal ribs, if present, in this septum); hypobranchial muscles distinct; extend from pectoral girdle to visceral arches; longitudinal orientation; coracomandibularis responsible for opening of jaw; extrinsic eye muscles; 4 rectus muscles (anterior, posterior, superior, inferior); 2 oblique muscles (superior and inferior); 3rd cranial nerve – anterior, superior, inferior recti and inferior oblique (premandibular myotome); 4th cranial nerve – superior oblique (mandibular myotome); 6th cranial nerve – posterior rectus, derived from both mandibular and hyoidean myotomes
Tetrapods – several trends evident in evolution of the axial musculature of vertebrates: in fishes the axial muscles are the main propulsive muscles and the most massive of the body, in tetrapods the appendicular muscles enlarge and the axial musculature diminishes
Amphibians (axial musculature transitional between that of fishes and reptiles) – epaxial muscles (dorsalis trunci); conservative; hypaxial muscles; primitive on tail but on trunk more advanced; divided into three groups: Subvertebral group (below transverse processes; flexes the spine), Rectus abdominis muscle (ventral, between the girdles; ventroflxes body, supports viscera), Lateral group (3 sheetlike layers; support and compress body wall) – external oblique, internal oblique, transverses; pelvic girdle – stronger in amphibians than in fishes; since it has gained articulation with the spine it does not require musuclar support; pectoral girdle no longer articulates with the head and does not have an articulation with the spine, several muscles evolve to hold this girdle to trunk; hypobranchial muscles; generally like fishes, but fleshy tongue has important added derivatives
Reptiles and mammals – epaxial muscles, those in tail without myosepta, those in cervical region form in layers, those of trunk complex; higher tetrapods - superficial epaxial bundles form long muscles that extend over many body segments; deep bundles are still segmented; longest bundles: longissimus group lies on transverse processes of vertebrae; includes the longest epaxial bundles; subdivisions include: longissimus dorsi longissimus cervicis, longissimus capitis; iliocostalis group is lateral to longissimus & spinalis arises on ilium and inserts on dorsal ends of ribs or uncinate processes; spinalis group lies close to neural arches connects spinous processes or transverse processes with those several vertebrae anteriorly; shortest bundles - intervertebrals remain segmented connect processes (spinous, transverse, & zygapophyses) of adjacent vertebrae; hypaxial muscles; cervical and caudal regions similar to amphibians; on trunk the subvertebral group much reduced (except in lumbar area); lateral group has modifications on thorax; the transversus is excluded from thorax and external and internal obliques become the external and internal intercostal muscles (new function of ventilation of the lungs); muscles in shoulder region derived from lateral group of hypaxial muscles become more prominent: Serratus, Levator scapulae, Rhomboideus; Diaphragm found only in mammals is of hypaxial origin and is innervated by ventral rami of cervical nerves; Hypobranchial muscles are much the same as for amphibians, but altered by regression of gills and complicated by enlargement of larynx

21. Describe the hypobranchial and tongue muscles of tetrapods.
In amphibians, hypobranchial muscles are generally like fishes, but fleshy tongue has important added derivatives. In reptiles and mammals, hypobranchial and tongue muscles are much the same as for amphibians, but altered by regression of gills and complicated by enlargement of larynx. They function to stabilize the hyoid and larynx. The roots lingu- and glosso- mean tongue.

22. Describe the appendicular muscles of fish.
Appendicular muscles of fish are divided into dorsal mass of extensors (upward and forward), and ventral mass of flexors (downward and backward). These muscles have origins on the girdles (which are anchored within the axial musculature) and adjacent fascia.

23. Describe the dorsal and ventral muscle groups of the pectoral and pelvic limb as described on your muscle handout.
Pectoral limb –
Dorsal group – includes deltoid, latissimus dorsi, teres major, subcoracoscapularis, teres minor, triceps, forearm and hand extensors, cutaneous trunci = maximus
Ventral group – pectoralis, supracoracoideus, biceps brachii, brachialis, forearm, wrist, and digit flexors
Pelvic limb –
Dorsal group – iliofemoralis, iliofibularis, iliotibialis, femorotibialis, ambiens, puboischiofemoralis internus, ankle and foot extensors
Ventral group – puboischiotibialis, pubotibialis and flexor tibialis, adductor femoris, ankle and foot flexors

24. Characterize the branchiomeric muscles. What is their origin?
Branchiomeric muscles are associated with the pharyngeal arches, are a series of skeletal & smooth muscles, are adductors, constrictors, & levators operate jaws plus successive gill arches. They have a visceral origin.

25. Discuss the branchiomeric muscles of each pharyngeal arch per your muscle handout.
Muscles of the Mandibular Arch (first arch): in Squalus & other fish - operate the jaws (adductor mandibulae & intermandibularis); in tetrapods, muscles of 1st arch still operate jaws; adductors of mandible: masseter and temporalis, pterygoid, digastric
Muscles of the Hyoid Arch: move hyoid arch, aid in hearing (stapedial muscle), assist in moving lower jaw (e.g., digastric)
Muscles of 3rd & successive arches: in Squalus - constrictors above and below gill chambers plus levators (including the cucullaris) that compress and expand the gill pouches; in bony fish - muscles reduced; operculum plays important role in respiration; in tetrapods - muscles further reduced; primary muscles include: stylopharyngeus (Arch III) - used for swallowing, intrinsic muscles of the larynx or 'voicebox' (remaining arches), cucullaris - gives rise to trapezius, cleidomastoid, and sternocleidomastoid muscles of amniotes

26. Discuss the incidence, derivation, function and structure of electric organs.
Electric organs are found in more than 500 species of fish. They are primarily derived from muscle cells, but also from glands and nervous tissue. They function in communication, orientation, detection of prey, and offense or defense. Electric organs consist of large number of electric discs in vertical or horizontal columns. Each disc is a functional unit called an electroplax. Each electroplax is a modified multinucleate muscle fiber.

B. DIGESTIVE SYSTEM

1. Discuss the four overall processes occurring in digestion.
Ingestion – functions in receiving ingested food, eating
Digestion – stores food temporarily then reduces it physically and chemically
Absorption – absorbs the products of digestion
Waste elimination – eliminates the undigested waste

2. Characterize the development of the digestive system, including parietal peritoneum, visceral peritoneum, dorsal mesentery, and ventral mesentery.
The primitive gut is formed as a result of the head-tail and lateral folds of the embryo and the resulting incorporation of the dorsal aspect of the yolk sac into the intra-embryonic coelum. The primitive gut is enveloped by a mesentery that has a dorsal and a ventral aspect. The ventral mesentery degenerates during development with the exception of the foregut ventral mesentery, which develops into specialized structures. The dorsal mesentery has different names according to its position along the gut: mesoesophagus, mesogastrium, mesoduodenum, mesentery proper (distal duodenum, jejunum and ileum), mesocolon and mesorectum. The dorsal mesentery is formed by a double layer of mesothelium that suspends the gut from the dorsal wall of the foregut to the hindgut. A layer of mesothelium lines the whole coelomic cavity (future peritoneal cavity) forming the parietal peritoneum, that lines the somatopleure (body wall), and the visceral peritoneum, that lines the splanchnopleure (gut wall composed of mucosa, submucosa and two muscle layers).

3. Define peristalsis and segmentation.
The action of peristalsis looks like an ocean wave moving through the muscle. The muscle of the organ produces a narrowing and then propels the narrowed portion slowly down the length of the organ. Segmentation is a stationary mixing contraction.

4. List the four layers of a typical gut wall.
Mucosa, submucosa, muscularis, serosa

5. Discuss the anatomy and physiology of the following:
Oropharyngeal cavity – part of the throat at the back of the mouth between the soft palate and the epiglottis; oropharyngeal isthmus is the opening from oral cavity to pharynx bordered by velum, faucial pillars and tongue
Oral cavity – (mouth) – the mouth extends from the lips to the floor of the mouth to the roof is the hard palate
Tongue – can be divided into an anterior 2/3 and posterior third; the anterior (oral) portion has a variety of papillae for holding food for chewing and taste buds; the posterior third (pharyngeal) is smooth for swallowing
Oral (Paraoral) glands – three paired major salivary glands and numerous minor ones in the tongue and palate; major glands are parotid (more serous secretions), (sub)mandibular (mucinous secretions) and sublingual (mucinous secretions)
Teeth – each tooth has four main parts, including the following: enamel - the outer layer of the tooth, dentin - the inner layer and the main part of the tooth, pulp - part of the inside of the tooth that contains the nerve, root - the part of the tooth that secures it into the jaw.

6. Define the following dental terms:
Dentin – The main, hard bone-like part of a tooth, beneath the enamel and surrounding the pulp hamber and root canals
Enamel – The hard, calcareous substance covering the exposed portion of a tooth.
Pulp cavity – The central hollow of a tooth containing the dental pulp and including the root canal
Pulp – The soft tissue forming the inner structure of a tooth and containing nerves and blood vessels
Cementum – A bonelike substance covering the root of a tooth
Ameloblast – A cell of the inner layer of the enamel organ of a developing tooth that is involved in enamel formation
Odontoblast – One of the cells forming the outer surface of dental pulp that produces the dentin of a tooth
Acrodont – Having teeth attached to the edge of the jawbone without sockets
Pleurodont – Having the teeth attached by their sides to the inner side of the jaw, as in some lizards
Thecodont – Having the teeth inserted in sockets in the alveoli of the jaws
Polyphydont – Having several or many sets of teeth in succession
Diphydont – Having two successive sets of teeth, deciduous and permanent
Monophydont – Having but one set of teeth of which none are replaced at a later stage of growth
Homodont – Having or being teeth that are all of similar form
Heterodont – Having the teeth differentiated into incisors, canines, and molars
Incisor – A tooth adapted for cutting or gnawing, located at the front of the mouth along the apex of the dental arch
Canine tooth – Any of four teeth having a thick conical crown and a long conical root, adjacent to the distal surface of the lateral incisors, pointed for piercing and tearing
Premolar – One of eight bicuspid teeth located in pairs on each side of the upper and lower jaws behind the canines and in front of the molars; grinding teeth with 1-2 roots
Molar – A tooth with a broad crown used to grind food, located behind the premolars; grinding teeth with 3 roots

7. Examine the evolution of teeth.
The development of heterodont teeth is linked to chewing and to high activity. Although some fish do use teeth to process food, most non-mammals use teeth primarily for securing and holding food, which is quickly swallowed. Mammals also secure and hold their food, but in addition they usually shear, crush, or grind their food. These new functions are important because they speed digestion and greatly increase the diversity of foods that can be eaten. Mammals have thecodont teeth, which increases the strength of the teeth for chewing. These dental changes (and many other changes in oral structures) are associated with the increased activity of mammals: they needed more energy more quickly, so the rapid intake and digestion of food was advantageous. Homology between placoid scales (dermal) and teeth is evident.

8. Give the dental formula of a cow, cat and human.
Cow: 0-0-3-3/3-1-3-3 = 32
Cat: 3-1-3-1/3-1-2-1 = 30
Human: 2-1-2-3/2-1-2-3 = 32

9. Discuss the location and function of the pharynx and esophagus.
Pharynx – located in the throat; passageway of food into esophagus (and air into larynx/trachea);
swallowing mechanism (deglutition): chew food & mix with saliva into bolus at back of pharynx;
swallowing reflex triggered (involuntary)
Esophagus – passageway for food from pharynx to stomach; location: mediastinum; behind
trachea; many mucous glands; movement of food: gravity; peristaltic waves from esophagus meet gastro-esophageal sphincter muscle, sphincter muscle relaxes, food moves into stomach all at once

10. Define crop.
A crop is a pouchlike enlargement of a bird's gullet in which food is partially digested or stored for regurgitation to nestlings.

11. Describe the anatomy of the stomach, including pylorus, pyloric sphincter, greater curvature, lesser curvature, proventriculus, and gizzard.
Parts of Stomach: cardiac region - around esophagus; fundic region - large ballooned area; pyloric region - near duodenum: the pyloric region narrows into pyloric canal, the pyloric sphincter muscle lies between pylorus & duodenum; greater curvature – the boundary of the stomach that forms a long usually convex curve on the left from the opening for the esophagus to the opening into the duodenum; lesser curvature – the boundary of the stomach that forms a relatively short concave curve on the right from the opening for the esophagus to the opening into the duodenum; body; stomach in two parts – the proventriculus produces digestive enzymes; the gizzard may be muscular for grinding food; these two regions least distinctive in carnivorous birds, most distinct in granivorous species

12. List the four parts of the stomach for a typical ruminant.
Rumen, reticulum, omasum, abomasum

13. Discuss the overall gastric function. Define chyme.
The overall function is to receive, store, liquefy, and mix food. Chyme is the thick semifluid mass of partly digested food that is passed from the stomach to the duodenum.

14. Explain the function of gastric zymogenic, parietal and goblet cells.
Zymogenic cells – stomach cells that produce pepsinogen for the breakdown of protein
Parietal cells – stomach cells that produce HCl for protein breakdown and pepsinogen activation; are antimicrobial
Goblet cells – stomach cells that secrete mucus for stomach lining protection

15. Discuss the overall function of the small intestine.
The small intestine functions in chemical digestion. Most absorption occurs in the small intestine.

16. Identify the purpose of the typhlosole, coil, ceca, and villi.
The purpose of typhlosole, coil, ceca, and villi is to increase surface area for more efficiency in digestion.

17. List the three pars of a tetrapod small intestine.
Duodenum, jejunum, ileum

18. Name the parts and discuss the function of the large intestine.
Parts of Large Intestine: cecum - nearest ileum of small intestine; (appendix is a blind pouch in this region); colon - majority of length; rectum - distal region of colon in pelvic cavity; anal canal - narrowing of rectum & opening to outside; the large intestine functions in the formation and storage of feces, some water absorption, and fermentation in some herbivores

19. Examine the development of the liver and gall bladder.
The liver and gallbladder develop from foregut and midgut pouches

20. Locate the falciform ligament, bile duct, and lesser omentum.
The falciform ligament is a fibrous ventral band that separates the medial and lateral segments of the liver's left lobe.
Bile ducts are the excretory passages in the liver that carry bile to the hepatic duct, which joins with the cystic duct to form the common bile duct opening into the duodenum.
The lesser omentum is a fold of the peritoneum joining parts of the stomach and duodenum to the liver.

21. Locate and discuss the exocrine function of the pancreas. What are acinar cells?
The pancreas is located posterior to stomach on the left side. Acinar cells in the pancreas produce pancreatic juice. The enzymes secreted by the exocrine tissue in the pancreas help break down carbohydrates, fats, proteins, and acids in the duodenum. These enzymes travel down the pancreatic duct into the bile duct in an inactive form. When they enter the duodenum, they are activated. The exocrine tissue also secretes a bicarbonate to neutralize stomach acid in the duodenum (the first section of the small intestine).

22. Compare the cloaca of placental versus nonplacental animals.
The cloaca is the common posterior chamber of most vertebrates into which the digestive, urinary, and reproductive tracts all enter. A cloaca is found in most reptiles, birds, and amphibians; many fishes; and, to a reduced degree, marsupial mammals. Placental mammals, however, have a separate digestive opening (the anus) and urinogenital opening. The cloaca forms a chamber in which products can be stored before being voided from the body via a muscular opening, the cloacal aperture.

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