I. Structure
A. Cells grouped into tissues; tissues
can be grouped into organs; organs can
grouped into
organ systems
1. Four major
tissue types
a. epithelial and endothelial (epi = outside,
endo = inside)
b. connective
c. muscle
d. nerve
2. Epithelial
tissues
a. occur in tightly packed sheets - skin for example, and inside of organs
b. many different kinds of cells make up epithelial tissue (see book)
c. some can be excretory or glandular or absorbing cells
i. mucus is one such production
ii. absorbing cells line the digestive tract
d. some cells have cilia, i.e., in lungs to move dust out. Smokers
can
paralyze those cells, making it hard to expel material (hence smoker's
cough.
3. Connective
tissues
a. these bind and connect other tissues
b. cells not as tightly packed as epithelial cells
c. often suspended in a matrix material, which can be jelly-like, solid
or
liquid
d. loose connective tissue - 3 types
i. collagenous
1. made of protein collagen - most abundant
protein in animal world
2. collagen made into fibrils (3 collagen proteins twisted together)
3. some used to hold tissue to bone
ii. elastic
1. made of protein elastin
2. gives skin resiliency
3. old skin gets cross-linked, and then looses resiliency, gets
wrinkled
iii. reticular
1. highly branched, joins tissue to tissue
e. Specialized connective tissue
i. adipose - used to store fat. When
you get fat, you increase their
size, not their number. Number determined at birth in most cases.
ii. fibrous - two kinds
1. tendons - attaches muscle to bone
2. ligaments - attaches bone to bone at joints
iii. cartilage - collagen fibers embedded
in a rubbery matrix called
chondrin. Combination of fibers and
chondrin gives great
strength, but flexibility
1. examples: windpipe, nose, discs in vetebra, caps on ends of bone
iv. bone - collagen fibers embedded in a solid
matrix of minerals.
1. matrix is CaPO4 (hydroxyapatite) and CaCO3 (calcium
carbonate)
2. gives bone great strength without being brittle
3. bone marrow is alive - site of blood cell synthesis
v. blood - cells in a liquid (plasma) matrix
1. plasma is a solution of salts, proteins,
and water
4. Muscle
- most abundant tissue type
a. three major kinds of muscle
i. skeletal
1. voluntary muscles - we have control over
their function
2. also called striated because of their striped appearance
3. can be fast reacting, but fatigue quickly
ii. smooth - also called visceral
muscles
1. involuntary muscles - often contract without our thinking about it
2. include muscles in intestines, throat, chest while breathing
3. slow response, but can sustain contractions for a long time
iii. cardiac
1. muscles of the heart
2. cells interdigitated with each other (tightly connected)
3. cells contract at intervals
5. Nervous
tissue - sensory tissues
i. functional unit is the neuron, or nerve cell
B. Organ Systems - combinations of
tissues working together
1. skin is
an organ - weighs about 9 lbs, has a surface area of about 15-20
square yards!
2. Organs
can be grouped into systems - humans have about 10-11 systems:
a. Integument
b. muscular
c. skeletal
d. nervous
e. endocrine
f. circulatory
g. lymphatic
h. respiratory
i. digestive
j. urinary
k. reproductive
C. Body Forms
1. Early animals
were flat - used surface of their body for gaseous exchange.
Planaria are one example.
2. As animals
became thicker, exchange surfaces had to be internalized, and
folded. Large areas needed to get enough materials exchanged.
If you
flattened out your lungs they would be the size of a tennis court (100
m2).
Your intestines, a baseball diamond!!
II. Digestion
A. Unicellular organisms - digest
food inside special food vacuoles. Engulf food
by phagcytosis
(surround and bring across cell membrane).
B. Multicellular organisms - have
a food cavity of some sort - anus and mouth
the same in
primitive organisms, separate in higher organisms (thank
goodness!!).
1. Hydra
- primitive - food comes in oral cavity, is digested outside in the
cavity, then absorbed across cell membranes.
2. Humans
- food goes in mouth, passes down digestive tract, nutrients
absorbed, wastes excreted out anus. One of the most primitive organisms
with this strategy is the earthworm.
C. Internal Environment
1. Small organisms
can't control internal environment easily.
2. Poikilotherms
- organisms without internal metabolic control of body
temperatures
i. to keep cool they move out of sun, to keep warm, into the
ii. body temperature can be high, so saying these organisms are "cold
blooded" is a misnomer
Reptiles and fish are two examples
iii. Homeotherms - can regulate metabolically
their body temperature
Mammals and birds are two examples
III. Nutrition
A. Why digestion?
1. Because
the food we take in doesn't always have the right proportions
of nutrients that our bodies need
2. Need to
break food down into small particles so they are more easily
absorbed
i. much of what we eat consists of large organic molecules - proteins,
carbohydrates, fats, nucleic acids
ii. small particles have a higher surface to volume ratio - allows more
sites for digestive enzymes to work
B. Calorie - same as 1000 kcal used
by chemists
1. Oxidation
of 1 gram of fat yields 9.5 kcal. About twice that of protein.
2. All organisms
use energy for
i. maintenance - keeping cells alive
ii. growth - adding new cells
3. Basal
Metabolism Rate (BMR) - resting metabolic rate
i. is inversely proportional to body size
- larger animals have a lower BMR
than small ones.
ii. poikilotherms of the same body weight have a lower BMR than
homeotherms - reason why snakes and reptiles can go long periods
without eating
4. Typical
BMR's for males: 1600-1800 kcal/day; female 1300-1500/day
i. about equivalent to 1 day's energy use by a 100 W lightbulb
5. Definitions:
i. Undernourished - taking in too few calories
ii. Malnourished - lacking essential nutrients
a. essential - means that we need to ingest
it - body can't make it
6. There are
four classes of nutrients:
i. essential amino acids
a. humans need 20 amino acids, of which 8 are essential
b. vegetarians need to be careful they get all the essential amino acids
ii. essential fatty acids
iii. vitamins
a. vitamins are organic
(contain carbon) compounds needed in very
small amounts - humans need 14 different vitamins
b. there are two kinds
1. water soluble
- Vit C is one
(ascorbic acid)
- can't build up very
high levels of these types because they end up going out in your
urine
a. lack of Vit C leads to scurvy
(inability to synthesize collagen)
eventual death (leading cause of death on ships 250 years ago)
b. Vit C and Vit E act as anti-oxidants - get rid of toxic oxygen
molecules (peroxide, OH radicals, etc.)
2. fat soluble
- Vit E is one
of these - can build up to toxic levels -
should be careful of taking too much
c. most people don't need vitamins if they are healthy
iv. minerals - inorganic
compounds needed in small amounts
a. N, P, K, Fe, etc.
b. Ca - needed for bones; Fe - needed for blood; P for making ATP;
IV. Digestion System (see in-class
handout for details)
A. The organs
involved are:
1. mouth
2. esophagus (throat)
3. stomach
4. gallbladder
5. pancreas
6. liver
7. intestines (both small and large)
8. anus and rectum
B. Follow the food!
1. Mouth -
saliva first step in digestion
a. saliva does 3 things
1. partially breaks down food using alpha-amylases
(break starches
down)
2. lubricates food with a mucilage (mucin)
so it slides down easier
3. contains buffers and anti-bacterial compounds
so acidity is
neutralized and many bacteria are killed before they enter your
stomach
4. Humans produce about 1 liter of saliva per day!! Cows, about 40
gallons!
b. Teeth masticate (break down) food into small particles - tongue helps
mix everything together into a mush called a bolus
2. Esophagus
a. Involuntary muscles push bolus down to stomach
b. Contractions are called peristaltic contractions
- like squeezing a tube
of toothpaste.
c. This is what enables you to swallow up-side-down! Gravity is NOT
used
to get food to the stomach.
3. Stomach
- see handout.
a. about 2 liter capacity
b. inner walls have many folds, called rugae
- increases surface area and
allows stomach to stretch when filled with food
c. endothelial cells on inner wall secrete gastric juices
i. HCl - which lowers stomach pH to 2.0 (like
vinegar, or coca-cola!)
pH in stomach is low enough that it can dissolve metal nails!
ii. low pH helps kill pathogenic bacteria, and breaks down food
iii. pepsinogen - a precursor peptide.
In presence of HCl, a portion is
cleaved off, and it becomes pepsin, a digestive
enzyme
iv. Pepsin hydrolyzes (breaks down) proteins to amino
acids
v. How come stomach doesn't attack itself?
1. mucus cells - lining inner wall are cells
that produce a mucus that
protects the stomach against its own gastric juices
vi. Where do the gastric juices come from?
1. parietal cells - these cells secrete the
HCl
2. chief cells - these secrete the pepsinogen
a. when a protein is secreted that is inactive, as pepsinogen is,
but which becomes
4. Stomach
and Intestines functioning- see handout.
a. stomach secretes a protein called intrinsic factor
(IF). This helps
in the absorption of Vitamin B12, which is necessary for the
formation of red blood cells.
b. stomach also readily absorbs alcohol and aspirin - but major
digestion does not take place here - that occurs in intestines.
5. Liver important for regulating blood sugar (keeps it constant at 0.1%).
a. when sugar levels are high, sugar taken out and stored as glycogen.
b. when sugar levels low, glycogen broken down into sugar.
6. Be sure
to know other details of digestion discussed in your book. |