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Respiratory system

The respiratory system's function is to allow gas exchange to all parts of the body.

The space between the alveoli and the capillaries, the anatomy or structure of the

exchange system, and the precise physiological uses of the exchanged gases vary

depending on the organism. In humans and other mammals, for example, the

anatomical features of

the respiratory system

include airways, lungs,

and the respiratory

muscles. Molecules of

oxygen and carbon

dioxide are passively

exchanged, by diffusion,

between the gaseous

external environment and

the blood. This exchange

process occurs in the

alveolar region of the

lungs.[1]

Other animals, such as

insects, have respiratory

systems with very simple

anatomical features, and in amphibians even the skin plays a vital role in gas

exchange. Plants also have respiratory systems but the directionality of gas

exchange can be opposite to that in animals. The respiratory system in plants also

includes anatomical features such as holes on the undersides of leaves known as

stomata.

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Fish Respiratory System

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Head of herring with operculum cut away

to reveal gills. There are usually 4 gills on each side

Gill filaments (detail)

The thousands of fine branches on each filament expose a large surface area to the water. Blood circulates in the filament branches and is separated from the water by a thin epithelium so that oxygen and carbon dioxide diffuse through

Breathing current

Water is taken in through the mouth, passes over the gills and is expelled via the operculum. Movements of the mouth floor and operculum create the current and the ‘valves’ (skin flaps)

skin flaps prevent return of water

circulatory system The heart pumps blood forward in the ventral vessel and through the gill filaments where oxygen is absorbed and carbon dioxide expelled. The dorsal vessel carries oxygenated blood to all parts of the body

gillsoperculum gullet

vertebral

dorsal blood vesselcirculation

ventral blood vessel

heart

capillary circulation in tissuesgut

mouth

gill bar

gill filaments

Breathing current

Circulatory system

air bladder (maintains buoyancy)

JAMALULHASLINA BINTI FUAD

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LIVE AND LIVING PROCESSES (SCE3101)

Insects Respiratory System

Air enters the respiratory system of most insects through a series of external

openings called spiracles. These external openings, which act as muscular valves in

some insects, lead to the internal respiratory system, a densely-networked array of

tubes called trachea. The tracheal system within an individual is composed of

interconnecting transverse and longitudinal tracheae which maintain equivalent

pressure throughout the system. These tracheae branch repeatedly, eventually

forming tracheoles, which are blind-ended, water-filled compartments only one

micrometer in diameter.[8] It is at this level of the tracheoles that oxygen is delivered

to the cells for respiration.

Insects were once believed to exchange gases with the environment continuously by

the simple diffusion of gases into the tracheal system. More recently, however, large

variation in insects ventilatory patterns have been documented and insect respiration

appears to be highly variable. Some small insects do demonstrate continuous

respiration and may lack muscular control of the spiracles. Others, however, utilize

muscular contraction of the abdomen along with coordinated spiracle contraction and

relaxation to generate cyclical gas exchange patterns. The most extreme form of

these patterns is termed discontinuous gas exchange cycles (DGC).

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Human Respiratory System

The human respiratory system consists of the lungs and tubes associated with the

lungs. It is located in the thorax or chest. The thorax is surrounded by the ribs. The

diaphragm forms the base of the thorax.

Contractions of the diaphragm and the intercostals muscle change the size of the

thorax and, thus, cause air to move in and out of the lungs.

The main job of the respiratory system is to get oxygen into the body and get waste

gases out of the body. It is the function of the respiratory system to transport gases

to and from the circulatory system.

Parts of the Respiratory System

The human respiratory system consists of the nose, nasal cavity, pharynx, larynx, trachea, smaller conducting passageways (bronchi and bronchioles), and lungs.

The Nose or Nasal Cavity

As air passes through the nasal cavities it is warmed and humidified, so

that air that reaches the lungs is warmed and moist.  The Nasal airways

are lined with cilia and kept moist by mucous secretions. The combination

of cilia and mucous helps to filter out solid particles from the air an Warm

and moisten the air, which prevents damage to the delicate tissues that

form the Respiratory System. The moisture in the nose helps to heat and

humidify the air, increasing the amount of water vapor the air entering the

lungs contains. This helps to keep the air entering the nose from drying

out the lungs and other parts of our respiratory system. When air enters

the respiratory system through the mouth, much less filtering is done.  It

is generally better to take in air through the nose.

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JAMALULHASLINA BINTI FUAD

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LIVE AND LIVING PROCESSES (SCE3101)

To review: his nose does the following:

1.                Filters the air by the hairs and mucous in the nose

2.                Moistens the air

3.                Warms the air

The Pharynx         

The pharynx is also called the throat. As we saw in the digestive system, the

epiglottis closes off the trachea when we swallow. Below the epiglottis is the larynx

or voice box. This contains 2 vocal cords, which vibrate when air passes by them.

With our tongue and lips we convert these vibrations into speech. The area at the top

of the trachea, which contains the larynx, is called the glottis.

The Trachea

The trachea or windpipe is made of muscle and elastic fibers with rings of cartilage.

The cartilage prevents the tubes of the trachea from collapsing. The trachea is

divided or branched into bronchi and then into smaller bronchioles. The bronchioles

branch off into alveoli. The alveoli will be discussed later.

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The Lungs

The lungs are spongy structure where the exchange of gases takes place. Each lung

is surrounded by a pair of pleural membranes. Between the membranes is pleural

fluid, which reduces friction while breathing. The bronchi are divided into about a

million bronchioles. The ends of the bronchioles are hollow air sacs called alveoli.

There are over 700 million alveoli in the lungs. This greatly increases the surface

area through which gas exchange occurs. Surrounding the alveoli are capillaries.

The lungs give up their oxygen to the capillaries through the alveoli. Likewise, carbon

dioxide is taken from the capillaries and into the alveoli.

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Gas Exchange

Body cells use the inhaled oxygen gotten from the alveoli of the lungs. In

turn, they produce carbon dioxide and water, which is taken to the alveoli

and then exhaled. These exchanges occur as a result of diffusion. In each

case the materials move from an area of high concentration to an area of

lower concentration.

The alveoli are well suited for the important job they have. There are about

300,000,000 alveoli per lung! That means there is a great surface area for gas

exchange. Also, the walls of the alveoli as well as the capillaries are very thin so that

the gases can diffuse readily.

When the blood picks up the diffused gases the gases are carried to their

destinations. Most of the oxygen is carried by the hemoglobin in the red blood cells

with only a small % dissolved in the plasma. Carbon dioxide and water are carried in

the plasma of the blood.

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The Mechanism of Breathing

Inspiration or inhalation is said to be an active process because it involves muscle

contraction. The diaphragm and intercostals muscles contract. The contracting

diaphragm flattens and stretches the elastic lungs downward. The contracting

intercostals pull the ribcage up and out causing the elastic lungs to stretch. The

expanding lungs cause the air inside to expand (a gas will always fill its container).

The expansion of air causes a drop in air pressure in the lungs. The air in the lungs

is at a lower pressure than the air outside. Air flows from higher to lower pressure so

air flows into the lungs from outside.

Expiration or exhalation is said to be a passive process because it does not involve

muscle contraction. The diaphragm and the intercostal muscles relax. The deforming

force on the elastic lungs has been removed. The lungs recoil elastically reducing

their volume – a passive process. The volume of air in the lungs decreases causing

an increase in the air pressure. The air in the lungs is at a higher pressure than the

air outside. Air flows from higher to lower pressure so the air flows out of the lungs.

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The elastic recoil of the lungs pulls up the adhering diaphragm and drags in the

adhering ribcage.

Breathing is normally under

unconscious control. We don’t have

to think about breathing. Exercise

increases the rate of breathing. The

brain detects a large increase in

carbon dioxide and increases the

rate of breathing. Now, exhalation,

which is normally passive, becomes

active. Other times when we control

our breathing rate is in speaking,

singing, or swimming.

Breathing is always controlled by

the brain’s detection of carbon

dioxide in the blood. When carbon

dioxide is in the blood the pH of the

blood is slightly lowered. The brain

detects this slight drop and sends

impulses to the diaphragm and

intercostal muscles. Thus, our breathing mechanism is controlled by rising levels of

carbon dioxide, not low levels of oxygen. Just as the level of carbon dioxide controls

the stomata opening in leaves it also controls our breathing.

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JAMALULHASLINA BINTI FUAD

710501095092

LIVE AND LIVING PROCESSES (SCE3101)

PRACTICAL 4 : RESPIRATORY SYSTEM OF FISH, INSECT AND

MAMMAL

Objectives : (1) To train students to dissect fish, insect and small

mammal.

(2) To train students how to use dissecting instruments.

(3) To increase students’ skill in displaying, drawing and

labeling respiratory organs.

(4) To enable students to examine the structures of the main

organs involved in respiration (lung, trachea, diaphragm,

rib cage and intercostal muscles)

(5) To increase students’ understanding of the process of

gas exchange in animals.

Material and apparatus:

Rats/guinea pig/white mice

Cockroach

Bony fish

Dissecting instruments

Dissecting board

Dissecting microscope

Hand lens

Transparent plastic ruler

Thread

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Procedure:

(a) Dissection of the fish respiratory system

1. The shape of the fish was observed: streamlined, neck less, paired fins and

flexible tail.

2. What was the advantage of having such shape?

The thin width helps it slice through the water quickly, and it also thin tail

helps it propel itself through the water.

3. Fish bodies were covered with scales. What was the function of the scales?

Scales serve a primarily protective function.

4. Bony fishes had a movable operculum or gill-cover protecting the gills on each

side of the body. The operculum was cut on one side to expose the gills. How

many pairs of gill can be found?

Four pairs.

5. The gills were mounted on bony structures called gill arch. Each complete gill

consisted of a bony gill arch supporting two rows of delicate gill filaments. The gill

filaments were examined under the dissection microscope, drawn and labeled.

What were the blood vessels found in the gill filaments?

The pillar cells of the lamellae, the interlamellar vessels in the filament and

the small vessels in the filament and arch.

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JAMALULHASLINA BINTI FUAD

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6. Gaseous exchange took place in the gill filaments. Describe the characteristic of

the gill filament so that an efficient gaseous exchanged can happen. Explain the

function of the gill filament.

Fish have developed gills for respiration which have:

large surface area which is needed for more oxygen to get in.

high blood flow

small/short diffusion distances

contain 4 gill arches (Bony fishes

each gill arch has 2 rows (hemibranchs) of gill filaments

each gill filament has many lamellae

The function of the gill filament extracts oxygen from the water to use in

processes like respiration.

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JAMALULHASLINA BINTI FUAD

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LIVE AND LIVING PROCESSES (SCE3101)

(b) Dissection of the cockroach respiratory system

External anatomy

1. The cockroach was killed using chloroform in the killing jar.

2. The cockroach was taken and identified the segmented body parts.

3. The head, thorax and abdomen were drawn and labeled. The number of

segments that make up the head, thorax and abdomen were counted.

4. The exoskeleton was made up of the hard and waxy chitin layer. Where could

you find the legs attached to?

Each thoracic segment bears a pair of walking legs on the ventral side.

5. The wings were opened up. What was the different between the two pairs of

wing and what their functions were?

The mesothorax and the metathorax bear each, a pair of wings. The

anterior pair of wings, called forewings are used as wing covers for the

posterior pair of wings called hindwings, which are used for flight.

6. The spiracle at each side of the segment was observed. The number of

spiracles found on the thorax and abdomen were counted. Was there any

spiracle on the thorax?

There are two thoracic and eight abdominal spiracles on the body of

cockroach.

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JAMALULHASLINA BINTI FUAD

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Internal anatomy

1. The legs and wings of the cockroach were cut.

2. From the dorsal posterior to the anterior part were cut gently.3

3. The inner part was opened up and was observed under the dissection

microscope. Air would flow through the spiracles, tracheae and end up in very

fine tubules called tracheoles.

4. Some tissues were gotten and mounted on a slide. A drop of water was put

and the coverslip was lowered gently.

5. The tissues were examined under the microscope. The respiratory tract was

drawn and labeled. (tracheae and tracheoles).

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JAMALULHASLINA BINTI FUAD

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LIVE AND LIVING PROCESSES (SCE3101)

(c) Dissection of the mammalian respiratory system

.

1. The rat was pinned to the dissecting board with the ventral surface uppermost.

2. A mid-ventral incision was made through the skin and was cut forward as far as

the lower jaw and then backwards to the anus.

3. Holding the skin with the forceps, the connective tissues between the skin and

the body was wall cut away as far as possible around the animal’s body and the

skin was pinned back.

4. The ventral and lateral thoracic walls were cut away to expose the thoracic cavity.

5. The thymus gland was removed.

6. Muscles and tissues of the neck were cut away to expose the trachea and larynx.

7. The larynx was cut above. The connective tissues attached to the trachea were

cut off.

8. The heart, lungs, trachea, esophagus and larynx were removed together.

9. The esophagus was carefully separated from the heart. The larynx, trachea and

lungs were pinned to the board.

10. A large labeled drawing of the structures I had taken out was made.

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JAMALULHASLINA BINTI FUAD

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Results:

Drawings and labeling

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Questions:

1. (a) How many pairs of ribs does this animal have?

12 pairs which consists of 7 pair "true" ribs and 5 pair "false" ribs.

The upper seven true

ribs (costae verae,

vertebrosternal ribs,

I-VII). are attached in

the front to the

sternum by means of

costal cartilage. Due

to their elasticity

they allow movement

when inhaling and

exhaling.

The 8th, 9th, 10th,

11th, and 12th ribs are called false ribs (costae spuriae,

vertebrochondral ribs, VIII-X), and join with the costal cartilages of

the ribs above.

The 11th and 12th ribs are also known as floating ribs (costae

fluitantes, vertebral ribs, XI-XII), as they do not have any anterior

connection to the sternum.

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JAMALULHASLINA BINTI FUAD

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LIVE AND LIVING PROCESSES (SCE3101)

(b) How does the rib cage function during gas exchange in this animal?

The movement of the rib cage is controlled by two main sets of

muscles, that is

the external

intercostal

muscles which

are found

between the ribs,

running

downward toward

the sternum and

the internal

intercostal

muscles which are found between the ribs, running at right angle to the

external intercostal muscles.

During inspiration, the external intercostal muscles contract while the

internal intercostal muscles relax. The rib cage is raised outwards and

upwards.

During expiration, the internal intercostal muscles contract while the

external intercostal muscles relax. The rib cage is pulled inwards and

downwards.

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JAMALULHASLINA BINTI FUAD

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LIVE AND LIVING PROCESSES (SCE3101)

2. (a) Describe the appearance and characteristic of the diaphragm.

The diaphragm is a dome-shaped musculofibrous septum that

separates the thoracic from the abdominal cavity, its convex upper

surface forming the floor of the former, and its concave under surface

the roof of the latter. Its peripheral part consists of muscular fibers that

take origin from the circumference of the inferior thoracic aperture and

converge to be inserted into a central tendon.

(b) What is the importance of this characteristic of the diaphragm in relation to its

function during gas exchange?

The diaphragm functions in

breathing. During inhalation,

the diaphragm contracts,

thus enlarging the thoracic

cavity (the external

intercostal muscles also

participate in this

enlargement). This reduces

intra-thoracic pressure: In

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JAMALULHASLINA BINTI FUAD

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LIVE AND LIVING PROCESSES (SCE3101)

other words, enlarging the cavity creates suction that draws air

into the lungs. When the diaphragm relaxes, air is exhaled by

elastic recoil of the lung and the tissues lining the thoracic cavity

in conjunction with the abdominal muscles, which act as an

antagonist paired with the diaphragm's contraction.

3. Describe the appearance of the left and right lungs. Squeeze the lungs and note its

texture. Place it in hot water. The air within the lung expands causing it to float.

The Left lung is divided into two lobes, an upper and a lower, by the oblique

fissure, which extends from the costal to the mediastinal surface of the lung both

above and below the hilum.

The Right lung is divided into three lobes (as opposed to two lobes on the left),

superior, middle, and inferior, by two interlobular fissures.

The lungs of mammals have a spongy texture and are honeycombed with

epithelium, having a much larger surface area in total than the outer surface

area of the lung itself.

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JAMALULHASLINA BINTI FUAD

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LIVE AND LIVING PROCESSES (SCE3101)

Resources :

http://en.wikipedia.org/wiki/Respiratory_system

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/Pulmonary.html

http://www.cdli.ca/~dpower/resp/main.htm

http://www.biotopics.co.uk/humans/resyst.html

http://www.coventry.ac.uk/ec//~nhunt/180sor/howgate/air.html

Mah Chee Wai and Dr. Tina Lim Swee Kim, (2008). Nexus SPM Biology. Petaling Jaya : Sasbadi Sdn Bhd.

http://www.umanitoba.ca/faculties/science/biological_sciences/lab16/

http://www.tutorvista.com/content/biology/biology-iii/animal-morphology/respiratory-excretory-nervous-reproductive-system-rat.php

https://www.msu.edu/course/lbs/158h/manual/Ratdissect.pdf

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