ZOO*2090 - Lab Flashcards
Lab
1
Q
What is a rasp?
A
Prominent feature in the mouth, located at the anterior end of a long, cartilage-supported tongue.
(lamprey)
2
Q
Pharynx divides into..? (2)
lamprey
A
- Dorsal esophagus
2. Ventral respiratory tube
3
Q
What is a velum?
A
Flap of tissue that will close off the respiratory tube
lamprey
4
Q
Internal gill slits lead from ____ to ___?
A
Lead from the respiratory tube to the gill pouches
5
Q
What happens in the gill pouches?
lamprey
A
In the gill pouches, O2 exchange occurs across the gill lamellae.
6
Q
Lampreys have external gill pouches.
True or False?
A
False.
7
Q
Lampreys have external gill slits.
True or False?
A
True.
8
Q
What is the lamprey nostril connected to?
Hint: internally
A
It is connected to the olfactory sac, which is connected to the hypophyseal pouch.
9
Q
What is the olfactory sac connected to? (Lamprey)
A
The olfactory sac is connected to the nostril (externally) and the hypophyseal pouch (internally).
10
Q
What is the function of a hypophyseal pouch?
A
Pouch acts like a pipette bulb to draw water through the nostril and into the olfactory sac.
(lamprey)
11
Q
What is the respiratory system flow of a lamprey?
A
Water –> into mouth –> velum –> respiratory tube –> internal slits –> gill pouches –> out of external slits
12
Q
A lamprey has a stomach. True or False?
How does digestive waste then leave the body?
A
False. food travels caudally from the esophagus directly into the intestine.
It leaves through the anus, located in the cloaca.
13
Q
A lamprey has a large liver. True or False?
A
True.
14
Q
What are the parts of a heart (of lamprey, perch, shark)? What kind of a circulatory system is it?
A
- Medial sinus venosus
- Atrium (sac-like)
- Ventricle (muscular)
- Conus Arteriosus
It is a single circuit circulatory system.
*Note: From conus arteriosus to ventral aorta.
15
Q
What are the internal gills? (sharks)
A
Internal gills are the respiratory organs of sharks.
16
Q
How many pairs of internal gill slits are there?
A
5 pairs.
17
Q
What are gill rakers? What is their function?
A
Gill rakers are small projections towards the openings of internal gill slits. They prevent large food particles from entering the gills.
18
Q
In sharks, gills are found of each side of an ___________.
A
In sharks, gills are found of each side of an interbranchial septum.
19
Q
In sharks, where is the site of gas exchange located?
A
In sharks, the actual site of gas exchange is the secondary lamellae, which are perpendicular to the primary lamellae.
Note that primary lamellae are attached to the septum.
20
Q
What is the pleuroperitoneal cavity and where is it located?
A
The pleuroperitoneal cavity is the portion of the coelom, it is the space surrounding the heart.
21
Q
What is the difference between the pleuroperitoneal cavity and the pericardial cavity?
A
They are both parts of the coelom surrounding the heart, but the pericardial cavity is located by the transverse septum.
22
Q
What are rugae (sharks) and where are they located?
A
Rugae are longitudinal folds which line the stomach.
23
Q
The shark esophagus is lined with small projections called esophageal _________.
A
The shark esophagus is lined with small projections called esophageal papillae.
24
Q
Give a flow chart of a shark digestive system.
A
Mouth –> pharynx –> esophagus –> stomach –> duodenum (receives bile from gall bladder & digestive enzymes from pancreas) –> ileum (spiral valve) –> colon –> rectum –> anus –> cloaca
25
The pancreas of Squalus has two pale, thin, connected lobes. What are they and where are they located?
1. Ventral lobe --> lies on the ventral surface of the duodenum
2. Dorsal lobe --> lies just caudal and dorsal to the stomach.
26
The Squalus spleen is a part of what system?
The spleen is a part of the circulatory system. It manufactures and stores blood cells.
27
What is the function of the rectal gland and where is it located?
The rectal gland is involved in salt excretion. It is located at the junction of the colon and the rectum.
28
What are aortic arches and how many pairs did primitive vertebrates possess?
Aortic arches are the arteries which leave the ventral aorta to take blood to the gills (to acquire oxygen), and from gills, they continue to converge at the dorsal aorta.
Primitive vertebrates had 6 pairs; these have been modified in different vertebrate groups.
29
What happened to the first aortic arch of the Squalus?
The Squalus lost the first aortic arch which originally went to the mandibular arch (visceral arch #1).
30
In sharks, oxygenated blood is collected from the gills by the _______.
In sharks, oxygenated blood is collected from the gills by the collector loops.
31
What are the portions of the collector loops, where are they located, and what is their function?
1. Pre-trematic branch, cranial portion of loop --> drains blood from gill lamellae in front of the gill slit.
2. Post-trematic branch, caudal portion --> drains blood from gill lamellae just behind gill slits.
32
Each collector loop leads to an ________, which all join to for the single _______, which takes the blood to regions of the body posterior to the gills.
Each collector loop leads to an efferent branchial artery, which all join to form the single medial dorsal aorta, which takes the blood to regions of the body posterior to the gills.
33
How does the shape of the myomeres in vertebrate (perch) differ from those in Branchiostoma?
The myomeres in Branchiostoma are unidirectional (all diagonal), whereas the myomeres in a perch are bidirectional (v-shaped).
34
What is an operculum (perch)?
An operculum is a bony flap which covers the gills.
35
What is the function of gill rakers?
Gill rakers help prevent debris flowing across the gill filaments.
36
What is a holobranch?
A holobranch is an arch with two sets of gill filaments.
37
What is the pyloric ceca?
The pyloric ceca is a group of glands with enzymes to help digestive tract (in perch). It is located near the beginning of the duodenum.
38
How does water flow through the perch?
Mouth --> buccal cavity --> pharynx --> gills --> out
39
What is the function of a swim bladder?
A swim bladder helps the fish stay afloat by filling it up with air.
40
Sharks do not have swim bladders. True or False?
True.
41
What are 4 ways that vertebrates eliminate wastes (nitrogen, salts, CO2, water)?
1. Kidneys
2. Gills
3. Integument
4. Salt glands
*Note: Process of elimination of wastes is intimately associated with the maintenance of the osmotic balance between organism and environment.
42
Generally, in most fishes, kidneys control the nitrogen excretion (ammonia and urea), while the gills control the water/ salt balance. True or False?
False.
Generally, in most fishes, kidneys control the water/ salt balance, while the gills control the nitrogen excretion (ammonia and urea).
43
What are the components of the urogenital system?
The urogenital system is composed of the urinary system and the reproductive system.
44
What is the nephric ridge and how is it associated with the kidneys?
The nephric ridge is a paired ridge of tissue that runs along the dorsal surface of the body cavity. Kidneys develop from this ridge.
45
Where are pronephric kidneys found?
Pronephric kidneys develop at the anterior portion of the nephric ridge.
**This is only found in embryos of vertebrates because it is a transitional form of kidneys.
46
Where are the opisthonephric kidneys found?
Opisthonephric kidneys develop from the middle and caudal portion of the nephric ridge.
47
What is an anamniote?
The "anamniotes" --> informal group comprising the fishes and the amphibians, which lay their eggs in water.
They are distinguished from the amniotes (reptiles, birds and mammals), which lay their eggs on land or retain the fertilized egg within the mother.
(google)
48
What kind of kidneys are found in amniote embryos? (transitional phase of kidney)
Mesonephric kidneys develop from the middle portion of the nephric ridge.
Is found in amniote development, degenerates into adulthood.
49
In amniote adults, the mesonephric kidney is replaced by the ...........?
Replaced by the metanephric kidney.
It is formed from the caudal portion of the nephric ridge.
*Note: metanephric kidney is drained by a duct called ureter.
50
The ducts that drain urine from the pronephric, mesonephric, and opisthonephric kidneys are all homologous. True or False?
What are these ducts sometimes called?
True.
These ducts are sometimes called archinephric ducts.
51
How is sperm carried to the cloaca in most male vertebrates? How does this change if the male has metanephric kidneys (therefore ureters)?
In all vertebrate males, archinephric ducts carry sperm to the cloaca. In males with metanephric kidneys, this is the exclusive function of the archinephric ducts, whereas if the kidneys are absent, the duct must is responsible for kidney extractions and sperm.
52
The reproductive system develops from...........?
The reproductive system develops from a genital ridge that arises from the medial edge of each kidney.
53
The nervous system changes severely across vertebrate classes. True or False?
False. The nervous system is very conservative and changes little.
54
The nervous system is composed of two systems. What are they and where are they responsible for?
1. Central nervous system --> brain and spinal cord
| 2. Peripheral nervous system --> cranial and spinal nerves, autonomic nervous system
55
What is a gonad?
Gonad --> organ that produces gametes (ovary, testis).
56
Does the lamprey have genital ducts?
| If yes, what is special about them?
There are no genital ducts in the lamprey.
57
Give the flowchart of the lamprey reproductive system.
(opisthonephric kidneys are lateral to the gonad)
| Gonads (testis, ovary) --> urogenital papilla --> coelom --> cloaca
58
What is the function of the urogenital sinus in sharks?
The urogenital sinus holds either sperm or urine.
59
Give a flowchart of the shark urinary system.
How does the flowchart change for mature male adults who have accessory urinary ducts?
How does the flowchart change for female sharks?
Opisthonephric kidneys --> opisthonephric duct --> urogenital sinus --> urogenital papilla (in cloaca)
If shark possesses accessory urinary duct:
Kidneys --> accessory duct --> cloaca
```
Female Shark (no sinus):
Opisthonephric kidneys --> opisthonephric duct --> urogenital papilla (in cloaca)
```
60
What is the mesorchium?
The mesorchium is a support system (mesentry) which supports the testis.
61
Give a flowchart of the reproductive system of a male shark/ perch.
Testes (supported by mesorchium) --> efferent ductules (embedded in mesorchium) --> modified kidney tubules --> opisthonephric duct --> seminal vesicule --> sperm sac (at caudal end of seminal vesicle) --> urogenital sinus (within urogenital papilla) --> surface of clasper
*the Siphon is a muscular sac under the skin on the ventral surface of each pelvic fin with facilitates the movement of sperm down the clasper groove by forceful expulsion of seawater.
62
Give a flowchart of the reproductive system of a female shark.
Ovaries --> coelom --> ostium (opening of oviduct) --> oviduct --> nidimental / shell gland (along oviduct) (sperm can be stored here) --> ovisac
*Note: when sperm meets the egg in the nidimental glad, the gland lays down a thin membranous that covers several ova (called a candle), which continues down the oviduct.
63
What are the ampullae of Lorenzini and what are they connected to?
Ampullae of Lorenzini are special sensing organs called electroreceptors, forming a network of jelly-filled pores. (Usually on the face)
Sharks have many of these small pores that lead to the lateral line system of canals.
64
What is the function of sensory receptors?
They convert environmental stimuli to nervous impulses. Impulses are relayed to the central nervous system where they are interpreted.
65
What is the evolutionary significance of sensory organs?
The need to integrate information from sense organs led to the expansion & differentiation or the anterior end of the spinal cord.
This formed the brain.
66
The _____ is derived from the pineal eye in sharks.
It is located.....
It arises from the ____, the dorsal surface o the diencephalon.
The epiphysis is derived from the pineal eye in sharks.
It is located towards the top of the brain, between the cerebral hemispheres.
It arises from the epithalamus, the dorsal surface o the diencephalon.
67
Where is the nephric ridge located?
On top of the notochord.
68
What are the three basic regions of the brain? Where are they located?
- Prosencephalon (forebrain)
- Mesencephalon (midbrain)
- Rhombencephalon (hindbrain)
69
What is the difference between sensory and motor nerve fibres?
Sensory --> afferent (receptor organs --> CNS)
| Motor --> efferent (CNS--> effector organs)
70
What is the function of the cerebrum (cerebral hemispheres)?
- integrating sensory information
- Initiating motor impulses
- storing memories
71
What parts of the brain are considered the telencephalon?
- Olfactory bulb, tracts, lobes
| - cerebrum
72
Where is the diencephalon?
The diencephalon is located between the telencephalon and the mesencephalon.
73
What parts of the brain are considered the telencephalon?
- Olfactory bulb, tracts, lobes
| - cerebrum
74
Where is the diencephalon?
The diencephalon is located between the telencephalon and the mesencephalon.
75
The hypothalamus bears a projection called the _______ (pituitary).
The hypothalamus bears a projection called the hypophysis (pituitary).
76
Where is the mesencephalon?
The mesencephalon is located between the diencephalon and the metencephalon.
77
The hypothalamus bears a projection called the _______ (pituitary).
The hypothalamus bears a projection called the hypophysis (pituitary).
78
Where is the mesencephalon?
The mesencephalon is located between the diencephalon and the metencephalon.
79
What is the function of the optic lobes?
- Receive information directly from eyes
| - Form the lateral line system, cerebellum, olfactory epithelium, and skin.
80
What is the function of the cerebellum?
- Controls body equilibrium
| - Coordinates fine motor activity
81
Where are the auricles located and what is their function?
Auricles are located lateral to the main portion of the cerebellum.
They receive stimuli from the inner ear and lateral line system via the telencephalon, and send out signals to motor centers.
82
Where are the auricles located and what is their function?
Auricles are located lateral to the main portion of the cerebellum.
They receive stimuli from the inner ear and lateral line system via the telencephalon, and send out signals to motor centers.
83
What is the most posterior part of the brain? What is it mostly made up of?
The myelencephalon is mostly made up of the medulla oblongata.
84
Why do brain ventricles exist and what are they filled with?
Since brain is enlargement of the anterior end of nerve cord, ventricles act as interconnected hollow spaces filled with cerebrospinal fluid.
85
Why do brain ventricles exist and what are they filled with?
Since brain is enlargement of the anterior end of nerve cord, ventricles act as interconnected hollow spaces filled with cerebrospinal fluid.
86
What is the function of the cerebrospinal fluid?
- Cushions the brain and spinal cord from mechanical trauma
| - Exchanges metabolites with surrounding tissues.
87
What are the types of sensory receptors? (4)
- Mechanoreceptors
- Chemoreceptors
- Photoreceptors
- Electroreceptors
88
Where are chemoreceptors found?
Base of olfactory lamellae (within olfactory sac).
89
What is the cornea?
Transparent fibrous tunic over the front of the eyeball.
90
What is the cornea?
Transparent fibrous tunic over the front of the eyeball.
91
What is the suprachoroidea? Where is it located?
A layer of vascular connective tissue inside the suprachoroidea.
92
What is the choroid layer? What does it become at the front of the eye?
It is the vascular, pigmented layer beneath the suprachoroidea.
It becomes the iris in the front of the eyeball.
93
Why is the iris important?
The amount of light striking the retina is regulated by the diameter of the pupil (opening through iris).
94
Why is the iris important?
The amount of light striking the retina is regulated by the diameter of the pupil (opening through iris).
95
The otic capsule consists of the vestibule and three semilunar ducts. The ducts all end at swellings called ampullae which contain which kind of receptors?
Mechanoreceptors.
96
What is the function of the lateral line system?
Considered to be the sense of "distant touch".
| Canals of the system contain mechanoreceptors. When water enters canals, it sends signals to the receptors.
97
What kind of receptors are ampullae of Lorenzini?
| What is their primary role?
Electroreceptors.
| Primary role: detection of bioelectrical voltage changes generated by prey species.
98
What are the layers of the epidermis? (Top to bottom)
1. Stratum corneum (fully keratinized)
2. Stratum granulosum
3. Stratum germinativum
99
What are the layers of the dermis? (Top to bottom)
1. Stratum spongiosum
| 2. Stratum compactum
100
What do chromatophores do and where are they located?
Give colour in the skin.
| Located in the stratum spongiosum.
101
What is the major difference between the dermis of reptiles and amphibians?
```
Amphibians often have multicellular glands in the dermis.
Mucous glands (clear), poison glands (granular).
```
102
What are the various types of skulls?
1. Anapsid --> no openings in temporal region (thought to be a derived condition)
2. Synapsids --> 1 large opening in temporal region (mammals)
3. Euryapsids --> 1 small upper opening (found in extinct marine reptiles)
4. Diapsid --> 2 fenestrae in temporal region (many reptiles)
103
How did forelimbs, hindlimbs, and pectoral girdle evolve in tetrapods?
Forelimbs --> more locomotion
Hindlimbs --> become elongated for jumping and walking
Pectoral girdle --> becomes larger, attaches to more of the vertebral column, and more muscles because it's wider.
104
How did forelimbs, hindlimbs, and pectoral girdle evolve in tetrapods?
Forelimbs --> more locomotion
Hindlimbs --> become elongated for jumping and walking. appendicular muscles become more numerous and complex.
Pectoral girdle --> becomes larger, attaches to more of the vertebral column, and more muscles because it's wider.
105
The pelvic girdle is attached to the vertebral column of tetrapods. True or False?
True.
106
In tetrapods, the epaxial muscles are now called ________.
In tetrapods, the epaxial muscles are now called dorsalis trunci.
107
The hypaxial muscles of tetrapods can be divided into three groups. What are they and where are they located?
1. Subvertebrals --> just ventral of the vertebral column (flexes spine)
2. Rectus abdominis --> ventral between pectoral and pelvic girdles (flexes body ventrally)
3. Lateral group.
108
What are the three layers of the lateral group in tetrapods?
1. External obliques
2. Internal obliques
3. Transversus
109
Give a flowchart of the mudpuppy respiratory system.
Choanae (internal opening of nasal passage) --> pharynx --> glottis (slit-like opening on floor of pharynx) --> laryngotracheal chamber --> 2 bronchi --> lungs
110
Which is found on the caudal part of a shark, The pericardial cavity or the pleuroperitoneal cavity?
The pleuroperitoneal cavity.
111
What is the largest organ in the pleuroperitoneal cavity of the Necturus?
The liver.
112
Name 4 ways that the tetrapod circulatory system has evolved due to gravity.
1. Arterial blood pressure is higher. Blood can be pumped farther with every contraction.
2. Blood vessel walls are much thicker and more muscular. This prevents the distension of vessels.
3. Body parts have double blood supply and collateral blood circulation. If one supply is cut off due to posture, blood can still be obtained.
4. One-way valves. Prevents backflow into lower extremities.
5. Tall tetrapods have tight skin and connective tissue on legs. Prevents distension of extremities (blood pooling).
6. Blood vessels pass between muscles in extremities. Muscles act like auxiliary pumps for blood during muscle contraction.
7. Well developed lymphatic system. Collects lymph forced into interstitial spaces due to blood pressure.
113
What happened to the aortic arches in tetrapods?
| Hint: disappeared & changed function
- Aortic arches 1, 2, 5 disappeared.
- Aortic arch 3 --> carotid system (carries blood to head)
- Aortic arch 4 --> systemic arteries (carry blood through the aorta to body)
- Aortic arch 6 --> pulmonary arteries (carry blood to lungs)
114
What are the 5 characteristics of the Phylum Chordata?
1. Notochord
2. Dorsal, hollow nerve
3. Pharyngeal slits
4. Subpharyngeal glad
5. Post-anal tail
115
What are the three subphyla of Chordata?
1. Urochordata (tunicates/ sea squirts)
2. Cephlachordata (lancelets)
3. Vertebrata (vertebrates)
116
Phylum Hemichordata, Phylum Echinodermata, and Phylum Chordata are all referred to as _______.
This is because ......?
Referred to as deuterostomes, because the first opening of the embryo becomes the anus and a new opening is formed for the mouth.
117
What is an endostyle in tunicates?
It is a part of the adult that produces mucus to trap food particles.
It may be homologous to the subpharyngeal glad.
**Note: although the larva possesses endostyle, it doesn't feed during this time.
118
Where does gas exchange take place Urochordata (tunicates)?
Across the tissues if the ogartngeal bars.
119
What is the function of the excurrent siphon in tunicates?
It is the location through which metabolic wastes are emptied.
120
V-shaped Myomeres are muscle segments that cover the majority of Branchiostoma. They are separated by connective tissue partitions. What are the partitions called?
Myosepta.
121
What is the major skeletal structure in the cephalochordates?
The notochord.
122
What structure is dorsal to the notochord in Cephalochordata?
The hollow nerve cord.
123
Give a flowchart of the Brachiostoma digestive tract.
Water current created by wheel organ --> water with food brought past buccal cirri --> vestibule --> mouth --> velum --> pharynx --> pharyngeal bars (mucus traps food particles) --> epipharyngeal groove --> esophagus --> midgut diverticulum (liver-like function) --> ileocolic ring (food is mized) --> intestine --> anus
**Note: after pharyngeal bars, water goes through pharyngeal slits into the atrium.
124
Branchiostoma has an excretory system that consists of segmentally arranged ____ which remove nitrogenous wastes from the blood and release them into the atrium.
Branchiostoma has an excretory system that consists of segmentally arranged nephridia which remove nitrogenous wastes from the blood and release them into the atrium.
125
Sharks belong to what group?
Chondrichthyes.
126
Bony fishes belong to what group?
Osteichthyes.
127
What part of the body is expanded anteriorly to form a brain in a lamprey?
Dorsal hollow nerve cord.
128
Where is the pineal eye located on the lamprey? What is its function?
It is located just posterior to the single nostril.
| It is used to detect changes in light intensity.
129
What kind of papilla are found near the lamprey cloaca?
| What exists from the cloaca?
Urogenital papilla.
| Urine and gametes exist from the cloaca.
130
What are the nostrils on a shark called? Where do they lead?
Nares lead to the olfactory sac.
131
What are the different types of chromatophores? (4)
1. Melanophores (black/ brown/ red)
2. Xanthophores (yellow)
3. Erythrophores (red)
4. Iridophores (reflect light)
132
What are some functions of integument?
1. Protect the organism from mechanical stress.
2. Maintain an osmotic balance between organism and environment.
3. Provide colouration (sexual or camouflage purposes).
133
What kind of scales do sharks have?
Placoid scales. Very small, hooked structures found on cartilaginous fishes.
134
From where are bony fish scales derived?
They are dermally derived.
135
What are the tyles of scales found in Osteichthyes? (3)
1. Ganoid scales --> rhomboidal and opaque, constructed of enamel-like coating on top of an acellular bony base.
2. cycloid scale --> thin, somewhat transparent, smooth distal edge.
3. Ctenoid scale --> comb-like projections on distal margin.
136
What is the function of a branchial basket?
Provides support for the gills.
137
What is the difference between the trunk vertebrae and the caudal vertebrae in sharks?
Trunk vertebrae: Thicker, parts sticking out to hook onto muscles.
Caudal vertebae: Smaller, better locomotion.
138
What is the pectoral girdle in sharks made up of?
1. Coracoid bar
| 2. Scapular process
139
What do shark pterygiophores make up? What are the two types?
Make up the pectoral fin.
1. Radial pterygiophores
2. Ceratotrichia
140
What is the shark pelvic girdle made up of?
The Ischiopubic bar, with small lateral projection (iliac processes).
141
How have male pelvic radial pterygiophores been modified in sharks?
They have been modified to form the clasper.
142
What are the 3 major components that form a vertebrate skull?
1. Chondrocranium --> Floor and lateral walls of the braincase and the optic & olfactory capsules.
2. Dermatocranium --> dorsal aspect of the brain (in vertebrates possessing bone)
3. Splanchnocranium --> form the jaw, support the gills, support the tongue & larynx, contribute to ear bones (tetrapods).
143
The Squalus only has one braincase component. What is it?
The chondrocranium. It completely surrounds the brain of sharks and remains cartilaginous.
(i.e. no dermatocranium)
144
What is the snout of sharks supported by?
| Hint: part of the chondrocranium
The snout is supported by the rostrum.
145
The supraorbital crest of shark skulls is perforated by a series of small holes. What are these holes called and what is their function?
These holes are called foramina. Branches of the superficial ophthalmic nerve pass through the foramina.
146
How many pairs of gill slits (and gill supports) did primitive jawed vertebrates have?
Primitive jawed vertebrates had 6 pairs of gills and 7 pairs of gill supports (branchial arches). (splanchnocranium/ visceral skeleton)
147
Label the 7 visceral arches found in sharks.
1. Mandibular arch (palatopterygoquadrate = upper, Meckel's cartilage = lower).
2. Hyoid arch (in front of gills).
3-7. Branchial arches (gill support).
148
What are the types of tails that fish can have?
1. Homocercal (even)
| 2. Heterocercal (1 longer than other)
149
What are the main functions of a skeleton?
1. Attachment for muscles
| 2. Protect organs
150
Give examples of sense organs from each type of receptor.
1. Chemoreceptors (nose)
2. Photoreceptors (eyes)
3. Mechanoreceptors (Lateral line, ears)
4. Electroreceptors (ampullae of lorenzini)
151
What kind of nitrogenous waste do sharks produce?
Urea.
152
The trunk muscles of tetrapods are segmented and form discrete muscle groups. True or False?
False. The trunk muscles of tetrapods are non-segmented and form discrete muscle groups.
