Download Lecture #17 - Suraj @ LUMS

Lecture 17
Transport in Animals
Tissues:
• Most animal cells are organized into tissues.
• Cooperative unit of very similar cells that
perform a specific function.
• Tissue comes from Latin word meaning
“weave”.
• Cells of tissues may be held together by: Fibers
Glue-like substance Plasma membrane
structures.
• Tissue structure is related to its function.
Tissues
There are four main types of animal tissue:
1. Epithelial
2. Connective
3. Muscle
4. Nervous
Epithelial Tissue
• Cells are tightly fitted together in continuous
layers or sheets.
• Cover outside of body (skin), line organs and
internal body cavities (Mucous membranes of
digestive, respiratory, and reproductive
systems).
• Tight packaging allows tissue to act as a barrier
to protect against mechanical injury, infection,
and fluid loss.
• Two surfaces: Free surface: Exposed to air or
fluid. Bottom surface: Attached to underlying
tissues by a basement membrane, a dense layer
of protein and polysaccharides.
Epithelial Tissue
Can be classified based on two criteria:
A. Number of layers:
Simple: One layer.
Stratified: Several layers
B. Shape of cells:
Squamous: Flat cells.
Cuboidal: Cube shaped cells
Columnar: Column shaped cells
Example: Simple squamous epithelium
Stratified columnar epithelium
Epithelial Tissue Covers and Lines the Body and its Parts
A. Simple squamous
(Lung air sacs)
D. Statified squamous
(Lining esophagus)
B. Simple cuboidal
(Kidney tubes)
C. Statified columnar
(Lining intestine)
Epithelial Tissue
• Some epithelial tissues, such as mucous
membranes, absorb and secrete chemical
solutions.
• Mucous membranes:
– Digestive tract epithelium (mucous membranes)
secretes mucus and digestive enzymes.
– Respiratory tract epithelium secretes mucous that
helps trap dust particles before they reach the lungs.
Connective Tissue
• Relatively few cells surrounded by large
amounts of nonliving material (matrix).
• Cells secrete the matrix, which can be solid,
liquid, or gelatinous.
• Diverse functions. Mainly bind, support, and
connect other tissues.
Connective Tissue Binds and Provides Support
A. Loose Connective Tissue
B. Adipose Tissue
C. Blood
D. Fibrous Connective Tissue
E. Cartilage
F. Bone
Six Types of Connective Tissue in
Humans
1. Loose Connective Tissue: Most widespread connective tissue in
vertebrates. Loose matrix with fibers, packing material. Attaches
skin to muscles, binds and holds tissues and organs in place.
2. Adipose (fat): Pads and insulates body. Energy storage.
3. Blood: Fluid matrix (plasma) has water, salts, and proteins.
Red and white blood cells.
4. Fibrous Connective Tissue: Matrix of densely packed collagen
fibers. Strong and nonelastic. Found in: Tendons: Attach muscles
to bones. Ligaments: Attach bone to bone.
5. Cartilage: Rubbery matrix with collagen fibers. Found on end
of bones, nose, ears, and between vertebra.
6. Bone: Supports the body of most vertebrates. Solid matrix of
collagen fibers and calcium, phosphate, and magnesium salts.
Bone is harder than cartilage, but not brittle because of collagen.
Muscle Tissue
• Most abundant type of tissue in most animals.
Accounts for two-thirds (2/3) of human weight.
• Specialized for contraction. Made up of long
cells that contract when stimulated by nerve
impulses.
• Muscle cells have many microfilaments made
up of actin and myosin.
• Muscle contraction accounts for much of
energy consuming work in animals. Adults
have a fixed number of muscle cells. Weight
lifting doesn’t increase number of muscle cells,
only their size.
Muscle Tissue
• There are three types of muscle tissue:
A. Skeletal (striated) muscle : Attached to
bones by tendons. Responsible for voluntary
movements.
B. Cardiac muscle: Forms contractile tissue of
heart. Not under voluntary control.
C. Smooth muscle: Found in walls of digestive
tract, bladder, arteries, uterus, and many
internal organs. Responsible for peristalsis and
labor contractions. Contract more slowly than
skeletal muscle, but can remain contracted
longer. Not under voluntary control.
Three Types of Muscle
B. Cardiac muscle
A. Skeletal muscle
C. Smooth muscle
Nervous Tissue
• Senses stimuli and transmits signals from one part of the
animal to another.
• Controls the activity of muscles and glands, and allows the
animal to respond to its environment.
• Neuron: Nerve cell. Structural and functional unit of
nervous tissue.
• Consists of:
Cell body : Contains cell’s nucleus.
Dendrite: Extension that conveys signals towards the cell
body.
Axon: Extension that transmits signals away from the cell
body.
Supporting cells: Nourish, protect, and insulate neurons.
Nervous Tissue Forms a Communication Network
Organs Are Made up of Different
Tissues
• Organ: Several tissues that act as a unit and together
perform one or more biological functions.
• Perform functions that component tissues can’t carry
out alone.
• Example: The heart is an organ made up of:
Muscle Tissue: Contraction.
Epithelial Tissue: Lines heart chambers to prevent
leakage and provide a smooth surface.
Connective Tissue: Makes heart elastic and strengthens
its walls and valves.
Nervous Tissue: Direct heart contraction.
Organs are Made of Several Different Tissues
Transport Systems
• Diffusion/passive transport and active
transport ways to exchange material.
• In larger complex organism cells separated
by each other and external environment.
• Need to transport nutrients, gases, and
wastes to and from cells.
• Need a system which can move substances
rapidly.
Transport Systems in Animals
•
•
•
•
Alimentary – food and water moved
Respiratory – air and water moved
Blood vascular – blood
Lymphatic - lymph
Components of A Circulatory System
• Blood: a connective tissue of liquid plasma and
cells.
• Heart: a muscular pump to move the blood.
• Blood vessels: arteries, capillaries and veins that
deliver blood to all tissues.
• 3 types – open system, closed system and
lymphatic system.
• Functions: Exchange gases with the respiratory
system. Supplies tissues with oxygen. Removes
carbon dioxide from tissues. Transports materials
(nutrients, hormones, etc.) inside body. Defends
against infection.
1. Open Circulatory Systems
• Common to molluscs and arthropods.
• Pump blood into a hemocoel with the blood
diffusing back to the circulatory system
between cells.
• Blood is pumped by a heart into the body
cavities, where tissues are surrounded by
the blood.
• The resulting blood flow is sluggish.
2. Closed Circulatory Systems
• Have the blood closed at all times within vessels
of different size and wall thickness.
• In this type of system, blood is pumped by a heart
through vessels, and does not normally fill body
cavities.
• Blood flow is not sluggish.
• Hemoglobin causes vertebrate blood to turn red in
the presence of oxygen; but more importantly
hemoglobin molecules in blood cells transport
oxygen.
• The human closed circulatory system is sometimes
called the cardiovascular system.
3. Lymphatic System
• Returns fluid and proteins that have leaked from
blood capillaries into tissues.
• Up to 4 liters of fluid every day.
• Fluid returned near heart/venae cavae.
Blood
Has 4 components:1. Plasma
2. Red Blood Cells
3. White Blood Cells
4. Platelets
1. Plasma
• Liquid component of the blood.
• 60% of blood is plasma.
• Plasma is made up of 90% water and 10% dissolved
materials including proteins, glucose, ions, hormones, and
gases.
• It acts as a buffer, maintaining pH near 7.4.
• Plasma contains nutrients, wastes, salts, proteins.
• Serum is plasma that no longer contains fibrinogen, a
protein involed in clotting.
2. Red Blood Cells
•
•
•
•
•
Also known as erythrocytes,
Flattened, doubly concave cells about 7 µm in diameter.
Carry oxygen associated in the cell's hemoglobin.
Mature erythrocytes lack a nucleus.
They are small, 4 to 6 million cells per cubic millimeter of blood,
and have 200 million hemoglobin molecules per cell. Humans have
a total of 25 trillion (about 1/3 of all the cells in the body).
• Red blood cells are continuously manufactured in red marrow of
long bones, ribs, skull, and vertebrae. Life-span of an erythrocyte is
only 120 days, after which they are destroyed in liver and spleen.
Iron from hemoglobin is recovered and reused by red marrow.
• The liver degrades the heme units and secretes them as pigment in
the bile, responsible for the color of feces.
• Each second 2 million red blood cells are produced to replace those
taken out of circulation.
3. White Blood Cells
• Also known as leukocytes,
• Larger than erythrocytes, have a nucleus, and lack hemoglobin.
• They function in the cellular immune response. White blood cells
(leukocytes) are less than 1% of the blood's volume.
• They are made from stem cells in bone marrow.
• There are five types of leukocytes, important components of the
immune system.
Neutrophils enter the tissue fluid by squeezing through capillary walls
and phagocytozing foreign substances.
Macrophages release white blood cell growth factors, causing a
population increase for white blood cells.
Lymphocytes fight infection. T-cells attack cells containing viruses. Bcells produce antibodies. Antigen-antibody complexes are
phagocytized by a macrophage.
• White blood cells can squeeze through pores in the capillaries and fight
infectious diseases in interstitial areas.
4. Platelets
• Platelets are cell fragments that bud off megakaryocytes in
bone marrow.
• Involved with clotting.
• They carry chemicals essential to blood clotting.
• Platelets survive for 10 days before being removed by the
liver and spleen.
• There are 150,000 to 300,000 platelets in each milliliter of
blood.
• Platelets stick and adhere to tears in blood vessels; they
also release clotting factors.
• A hemophiliac's blood cannot clot. Providing correct
proteins (clotting factors) has been a common method of
treating hemophiliacs. It has also led to HIV transmission
due to the use of transfusions and use of contaminated
blood products.
Electron Micrograph of Blood
Blood Clotting
•
•
•
•
•
•
•
•
•
•
Thromboplastin – lipoprotein released from injured tissue.
Clotting factors – enzymes in plasma.
Calcium ions.
Prothrombin catalysed to thrombin (protease).
Thrombin hydrolyses fibrinogen (large soluble protein) to
fibrin (insoluble).
Blood cells become trapped in the fibrin mesh and a clot
forms.
Dries and forms a barrier to prevent further blood loss.
Does not occur in undamaged blood vessels.
Heparin is an anticoagulant.
If clot forms in blood circulation it is called a thrombus,
leads to thrombosis.