Physiology Homeostasis: digestive, respiratory, circulatory, & excretory systems

PhysiologyPhysiology

Homeostasis: digestive, Homeostasis: digestive, respiratory, circulatory, & respiratory, circulatory, &

excretory systemsexcretory systems

PhysiologyPhysiology

• Homeostasis = the maintenance of stable internal conditions in spite of changes in the external environment.– Circulatory system– Respiratory system– Digestive system– Excretory system

Circulatory SystemCirculatory System• The circulatory system functions as the

body’s “transportation highway” for the following substances:Nutrients – come from the food we eatOxygen – comes from the air we breathMetabolic waste – created during some body

processesHormones – come from glands in our body and

are the trigger for certain body functionsHeat – helps to cool us off or heat us up

depending on what we need

Circulatory SystemCirculatory System• The circulatory system is composed of a

few important parts:Heart – the pump that sends blood moving

through the bodyArteries – blood vessels that send oxygenated

blood to the body from the heartVeins – blood vessels that send deoxygenated

blood to the heart from the bodyCapillaries – small blood vessels that allow

exchange of substances from the blood to the body and from the body to the heart

Circulatory SystemCirculatory System



• The heart is the muscular pump that cycles your blood. It is composed of 4 “chambers”:– left & right atrium and left & right ventricle

The atrium is responsible for receiving blood into the heart.

The ventricle is responsible for pumping blood out of the heart.

Circulatory System: breakdownCirculatory System: breakdown

• To the heart:– Veins – Deoxygenated blood

(in general)– atrium

• Away from the heart:– Arteries – Oxygenated blood

(in general)– ventricle


• Components that make up the blood:– Plasma = liquid portion of blood– Red blood cells (erythrocytes) =

responsible for carrying oxygen• Note: rbc’s have no nucleus!

– White blood cells (leukocytes) = defend the body against disease

• Note: there is 1 wbc for every 600 rbc!

– Platelets (thrombocytes) = help to clot blood • Note: become shaped like stars when clotting!

Blood CellsBlood Cells

Red Blood CellRed Blood Cell

White Blood CellWhite Blood Cell

Platelet Platelet

Respiratory SystemRespiratory System


Respiratory SystemRespiratory System– Pharynx = passageway for both air and food.– Larynx (voice box) = passageway for air

only.– Trachea (windpipe) = long tube leading to

lungs. Note: wrapped in rings of cartilage.

– Bronchus s. (bronchi p.) = two tubes separating from trachea, leading to each lung.

– Bronchiole = smaller branches of bronchi.– Alveoli = found at end of bronchioles, clusters

of air sacs where gasses are exchanged


• How do we breath?– The diaphragm, the flat muscle underneath

our lungs works by creating low pressure within our lungs. By contracting (inhalation) it moves down, creating more space in the lungs and lower pressure. This forces air to rush in to our lungs. When it relaxes (exhalation) it moves back up, forcing air out of our lungs.

BreathingBreathing

Digestive SystemDigestive System

• The digestive system is responsible for breaking down our food and extracting the nutrients and fluids from it.

• I believe you already know most of the organs of the digestive system so we will concentrate on those that you may not be familiar with.


• Amylase = enzymes that begin the breakdown of carbohydrates. These are contained in your saliva.

• Esophagus = long tube that connects mouth to stomach. Food doesn’t just fall into the stomach, it is pushed down through peristaltic motion:

peristalsisperistalsis

Digestive SystemDigestive System• The stomach breaks down food into

smaller pieces with the help of gastric fluids:

• HCl (hydrochloric acid) – breaks protein bonds

• Pepsin – unfolds proteins into single strands– Note: stomach is 3 million times more acidic

than your bloodstream!


• The small intestine is responsible for the majority of digestion and absorbing nutrients into your bloodstream.

• The pancreas, liver and gall bladder all secrete digestive enzymes into the small intestine, which help finish digestion by converting carbohydrates into monosaccharides, proteins into amino acids, and lipids into fatty acids.


• The small intestine absorbs nutrients more effectively with the help of villi. These increase the surface area of the small intestine so that there are more spaces for nutrients to be absorbed.

villi villusvilli villus


• Finally, the large intestine or colon is responsible for extracting water and mineral ions from the remaining material. All indigestible material is then excreted as feces; first compacted in the rectum, then expelled through the anus.

Length of Digestive TractLength of Digestive Tract

• Total = 8 m (26 ft) – about 2.3 days

• Mouth = 8 cm (3 in.) / 5-30 s

• Pharynx/esophagus = 25 cm (10 in.) / 5-10 s

• Stomach = 15 cm (6 in.) / 2-6 hours

• Small intestine = 4-6 m (13-20 ft) / 3-6 h

• Large intestine = 1.2 m (4 ft) / up to 2 d

Excretory SystemExcretory System

• The kidneys are the “filters” of blood.

• Also, when our bodies are metabolizing or processing nucleic acids and proteins, nitrogen is usually left over and must be gotten rid of.

• Nitrogen will form ammonia in our bodies which is toxic.

Excretory SystemExcretory System

• The liver will convert ammonia to urea, which is much less toxic. Once this happens it is transferred to the kidneys so that it can be removed from the body.

• The kidney has a few major structures:– pyramid– nephron

Kidney Kidney

Excretory SystemExcretory System• As blood flows through the kidneys is goes

through three main phases:Filtration = all non-useful substances are

allowed to pass through glomerulus and Bowman’s capsule, and useful substances are returned to the body with the blood.

Reabsorption & Secretion = any useful substance that got by filtration is reabsorbed and non useful substances are secreted.

Urine formation = water, urea and salts are then emptied into ureter.

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Physiology Homeostasis: digestive, respiratory, circulatory, & excretory systems