4. Organisms and Cells
■ Some organisms are unicellular.
– This means they are made of only one cell.
– Examples: bacteria, yeast
■ Some organisms are multicellular.
– This means they are made of many cells.
– Examples: humans, trees
■ Unicellular organisms have nothing but a single cell.
■ However, multicellular organisms have many more levels of organization to make sure the
whole body can work correctly, even when it is doing many things at the same time.
5. There are 5 Levels of Organization in
Multicellular Organisms:
■ 1. Cells
■ 2. Tissues
■ 3. Organs
■ 4. Organ Systems
■ 5. Organisms
6. The cell is the basic
unit of life.
Cells are specialized
by size and shape for
the job they do. The paramecium above is
made of only one cell and it
must perform all the jobs of
the organism.
Example: skin cell
The Cell
7. T I S S U E S
Tissues are made of the same type of cells grouped together to do a
specific job.
Example: Humans have
four kinds of tissue in their
Bodies: Epithelia, Muscle,
Connective, and Nerve.
8. Organs
Organs are made up of different
tissues that work together to do a
job.
Example: a heart is an organ.
9. Organ Systems
An organ system is a group of organs working together.
Examples:
• Human organ systems include circulatory, reproductive, digestive, nervous, respiratory.
• Plant organ system-roots, stems, leaves= transport system.
12. Tissues
Levels of organization:
– Cells Smallest
– Tissues
– Organs
– Organ Systems
– Organisms Largest
Tissues = group of similar cell types that perform
a common function.
Tissues = group of similar cell types that perform a
common function.
Four basic types of tissue:
1. Epithelial
2. Connective
3. Muscle
4. Nervous
13. Tissues - Epithelial Tissue
Epithelium is tightly packed
sheets of cells
■ cover organs and outer
surfaces
■ line insides of hollow
organs, vessels, and body
cavities.
Figure 16.1
(a) Examples of organs lined with epithelial
tissue:
(b) Epithelial cells in skin
Heart and blood vessels
Respiratory tract
Digestive tract
Urogenital tract
Epidermis
(c) Epithelial cells lining
the small intestine
14. Tissues - Epithelial Tissue
Epithelia are polar
■ anchored on one surface, but free on another
– The free side is typically exposed to the
environment or body fluids
§ Can be single layer or many
layers thick
§ Function in protection,
secretion, and absorption
§ Epithelial cells are continuously
sloughing off and are replaced
by cell division
15. Tissues - Connective Tissue
Connective Tissue
■ Loosely organized and composed of cells embedded in a matrix
■ Cells
– Examples include: Blood cells, adipocytes, fibroblasts, chondrocytes,
osteocytes
■ Matrix is composed of two things
1. Ground substance
■ May be liquid, gel-like, rubbery or solid
2. Fibers
■ Collagen, elastin, reticular fibers
16. Tissues - Connective Tissue
Connective Tissue
■ Usually binds organs or tissues to one another
■ Six different types:
1. Loose connective tissue
2. Adipose tissue
3. Blood
4. Fibrous connective tissue
5. Cartilage
6. Bone
17. Figure 16.2a
Tissues - Connective Tissue
■ Most widespread tissue in
animal body
■ Matrix composed of collagen
and elastin fibers
■ Cells are fibroblasts and
adipocytes
■ It is called “loose” because
fibers are loosely woven
together
■ Binds epithelia to tissues,
pads skin, and holds organs
in place
Loose Connective Tissue
18. Tissues - Connective Tissue
Adipose Tissue
■ AKA Fat
■ Primarily adipocytes; small amount
of matrix
■ Functions
– Used for storage of energy
(fat)
– Insulation
– Padding for organs
Figure 16.2b
19. Tissues - Connective Tissue
Blood
■ Cellular component
– red blood cells, white
blood cells and
platelets
■ Matrix is the plasma
■ Functions include
carrying oxygen and
nutrients; fighting
infection
Figure 16.2c
Red
blood cell
Platelet
White
blood cell
Plasma
(c) Blood
20. Tissues - Connective Tissue
Fibrous Connective Tissue
– Forms tendons and ligaments
– Matrix is collagen fibers
running in parallel
– Cells are fibroblasts
Figure 16.2d
Fibroblast
cell
Parallel
collagen
fibers
(d) Fibrous connective tissue (tendon)
21. Figure 16.2e
Matrix
Matrix
Chondro-
cytes
(e) Cartilage
(at the end of a bone)
Tissues - Connective Tissue
Cartilage
■ Cells are chondrocytes
■ Cells secrete rubbery
matrix, collagen and elastin
■ Cartilage cushions joints,
forms support for ears
and nose
■ Not vascularized, so takes
a long time to heal if injured
22. Figure 16.2f
Matrix
Osteocytes
Central
canal
(f) Bone
Tissues - Connective Tissue
Bone
■ Rigid connective tissue
■ Cells are osteocytes
■ Cells secrete matrix of
collagen fibers and calcium
salts
■ Bone marrow produces
blood cells
■ Body can make use of
calcium from bones if
dietary levels are too low
23. Tissues - Muscle Tissue
Muscle is contractile tissue
■ Long, thin cylindrical cells called muscle fibers
■ Two proteins – actin and myosin – interact to cause contraction of
muscle fibers
Three types of muscle:
1. Skeletal
2. Cardiac
3. Smooth
24. Tissues - Muscle Tissue
Skeletal Muscle
– Usually attached to bone
– Produces all voluntary
movements
– Striated – due to overlap
of actin & myosin
– Long, thin, cylindrical
shape
Figure 16.3a
Muscle fiber Nucleus
(a) Skeletal muscle (biceps)
25. Figure 16.3b
(b) Cardiac muscle (heart)
Muscle fiber Nucleus
Tissues - Muscle Tissue
Cardiac Muscle
■ Only found in
heart tissue
■ Striated
■ Involuntary,
undergoes
rhythmic
contractions to produce
heartbeat
■ Branched, interlocking cells
propagate signal to contract
almost simultaneously
26. Figure 16.3c
Muscle fiber Nucleus
(c) Smooth muscle (intestine)
Tissues - Muscle Tissue
Smooth Muscle
■ Not striated
■ Spindle-shaped cells
■ Musculature of
organs, blood
vessels, digestive
tract
■ Involuntary
■ Contracts more slowly and
for longer than skeletal
muscle
27. Tissues - Nervous Tissue
Nervous Tissue
■ Neurons conduct electrical signals
■ Primary cells of the brain and spinal cord
■ Main function of neurons is to:
– Sense stimuli
– Process stimuli
– Transmit signals
■ Most cells of nervous system do not undergo cell division
28. Tissues - Tissue Donation
Brain death and Tissue Donation
■ Injuries from motor vehicle accidents, burst blood vessels, and
drowning are common causes of brain death
– Once dead, brain cells cannot recover
– Other tissues can be harvested to help others
■ > One person’s tissues can improve the lives of as many as 50
people.
30. Figure 16.5
Organs and Organ Systems
■ Organs are composed of two or
more tissue types
– Organs that act together
form an organ system
– All the organ systems of a
body form an organism
Muscle cell
Muscle tissue
Heart organ Circulatory system Organism
32. Organs and Organ
Systems –
The Liver as a Model
Organ
■ The liver sits below the diaphragm
■ comprised of four lobes
■ associated with the gall bladder.
Figure 16.6
33. The Liver as a Model Organ
■ The liver is an important component of the circulatory and the digestive system.
– As part of the circulatory system, the liver:
■ Synthesizes blood clotting factors
■ Removes and breaks down toxins
■ Regulates blood volume
■ Destroys old red blood cells
– As part of the digestive system, the liver:
■ Metabolizes and stores nutrients
■ Produces bile
35. The Liver as a Model Organ
Liver transplants can be made from living donors or from brain dead
ones
– Unlike many organs, liver can regenerate itself
– Portion can be taken from living donor and implanted in
patient
– Liver in donor and patient will regrow to normal size
36. 1
2
3
4
5
6
7
Alimentary canal
Accessory organs
of the digestive
system
Liver
• Produces bile
which aids
absorption of
fats
Mouth
• Teeth reduce the size of food,
increasing surface area available
for digestion by enzymes.
• Enzymes in saliva then start
breaking down carbohydrates.
Gall bladder
• Stores bile and empties
into small intestine
Pancreas
• Produces digestive
enzymes
• Produces a buffer
that neutralizes
acidity of stomach
acid
Pharynx
• Epiglottis blocks the opening to the
windpipe when we swallow, so that our
food goes into our esophagus rather than
our lungs.
Esophagus
• The esophagus transports food to stomach
by rhythmic waves of muscle contractions
called peristalsis.
Stomach
• Acidic gastric juices start breaking down
foods.
• The enzyme pepsin breaks down proteins.
• Mucous prevents gastric juices from
digesting stomach.
• Pyloric sphincter regulates movement of
food from stomach to small intestine.
Small intestine
• Most digestion of carbohydrates, proteins,
and fats occurs here.
• Nutrients are absorbed into the
bloodstream.
Large intestine
• Water is reabsorbed.
Anus
• Undigested materials are excreted
as feces.
The Digestive System
Figure 16.8
37. The Digestive System
Figure 16.8
Mouth
• Teeth reduce the size of food,
increasing surface area available
for digestion by enzymes.
• Amylase enzymes in saliva
start breaking down
carbohydrates.
38. The Digestive System
Figure 16.8
Esophagus
• The esophagus
transports food to stomach
by rhythmic waves of
muscle contractions called
peristalsis.
Stomach
• HCl starts breaking down
foods.
• The enzyme pepsin breaks
down proteins.
• Mucous prevents gastric juices
from digesting stomach.
• Pyloric sphincter regulates
movement of food from stomach
to small intestine.
39. The Digestive System
Figure 16.8
Small intestine
• Most digestion of
carbohydrates, proteins,
and fats occurs here.
• Nutrients are absorbed
into the bloodstream.
Large intestine
• Water is reabsorbed
Internal Specializations
Mucosal folds, villi and
microvilli increase the
surface area of the
intestines to allow nutrient
absorption
40. The Digestive System
Figure 16.8
Accessory Organs
Liver
• Produces bile which
aids absorption of fats
Gall bladder
• Stores bile and
empties into small
intestine
Pancreas
• Produces LOTS of
digestive enzymes
• Produces a buffer
that neutralizes stomach
acid
• Enzymes & buffer are
released into small
intestine
41. 16.2 Organs and Organ Systems
Evolution of the Digestive System
■ Paramecia use digestive food vacuoles
■ Hydra have an extracellular digestive sac
■ Earthworms have alimentary canal
– Allows for ‘assembly line’ like specialization
Figure 16.9
