Homeostasis
● Homeostasis is the balance of the body’s internal environment
● Chemical level → Cellular level → .Tissue level → Organ level → System level
→ Organism
● Plasma membrane has selective permeability which means that is is permeable
to gases but impermeable to glucose.
● Feedback cycles are where a stimulus creates a response and a return to
original conditions.
● Positive feedback cycles are where the return condition increases the stimulus.
For example, account balance growns and, interest increases.
● Negative feedback cycles are the most common. For example, body temperature
rises, body sweats, body temperature drops.
,Connective Tissue
● 4 types of connective tissue. Connective tissue proper, Cartilage, Bone, Liquid
● 6 subdivisions
- Loose Connective Tissue located in outer blood vessels which bind organs
together and are made up of loose random fibres.
- Fibrous Tissue is located in ligaments and tendons which bind bones
together. They are densely spaced and contain parallel collagen fibres.
- Adipose is located around eyes and heart which store energy. They are
made up of fat filled adipocytes.
- Cartilage tissue is located in external ear and larynx. Eases joint
movements and made up of spaced out cells in cavities.
- Bone tissue is located in skeleton which supports body and organs and is
made up of widely spaced cells in a cavity.
- Blood is located throughout the cardiovascular system which transports
nutrients and is made up of white blood cells, red blood cells and platelets.
● Main components in connective tissue are
1) Ground substance
2) Cells
3) Fibres
● Collagen fibre is most common in animals, is strong and forms tendons.
● Elastic fibre which are long and thin which stretch like rubber bands. Located in
lungs and skin where elasticity are needed.
● Reticular fibre which is short and fine and are located in capillaries which provide
support and bring oxygen to tissues.
, Epithelial Tissue
● Functions include:
protection, absorption, secretion, excretion, filtration, sensory
● Cells are closely packed and hexagonal shaped
● Cell junctions that connect epithelial cells:
They are tight, impermeable and leak-proof
- Desmosome, button like anchors between adjacent membranes which prevent
cells from being pulled apart
- Gap junctions, connected by small cylinder type structures called connexions
which allow communication
● Simple - One layer, where thin surface is needed
● Stratified - Two or more layers, where abrasion is likely
● Squamous - Flattened disc shaped
● Cuboidal - Box like
● Columnar - Tall / Column shaped
● Simple Squamous
Thin and permeable
For lining and covering and a boundary for transport
Located in the alveoli of lungs
● Stratified Squamous
The surface cells are squamous
Keritised - full of keratin and are dead
Non-keratinised - lines the mouth and esophagus
● Simple cuboidal - secretion
● Simple columnar - absorption
● Stratified cuboidal / columnar
Ducts of larger glands such as mammary glands
Pharynx and urethra
● Epidermis of skin is made up of epithelial cells
● Dermis is made up of mainly connective tissue
● Nutrients in skin diffuse from the dermis to epidermis
● Homeostasis is the balance of the body’s internal environment
● Chemical level → Cellular level → .Tissue level → Organ level → System level
→ Organism
● Plasma membrane has selective permeability which means that is is permeable
to gases but impermeable to glucose.
● Feedback cycles are where a stimulus creates a response and a return to
original conditions.
● Positive feedback cycles are where the return condition increases the stimulus.
For example, account balance growns and, interest increases.
● Negative feedback cycles are the most common. For example, body temperature
rises, body sweats, body temperature drops.
,Connective Tissue
● 4 types of connective tissue. Connective tissue proper, Cartilage, Bone, Liquid
● 6 subdivisions
- Loose Connective Tissue located in outer blood vessels which bind organs
together and are made up of loose random fibres.
- Fibrous Tissue is located in ligaments and tendons which bind bones
together. They are densely spaced and contain parallel collagen fibres.
- Adipose is located around eyes and heart which store energy. They are
made up of fat filled adipocytes.
- Cartilage tissue is located in external ear and larynx. Eases joint
movements and made up of spaced out cells in cavities.
- Bone tissue is located in skeleton which supports body and organs and is
made up of widely spaced cells in a cavity.
- Blood is located throughout the cardiovascular system which transports
nutrients and is made up of white blood cells, red blood cells and platelets.
● Main components in connective tissue are
1) Ground substance
2) Cells
3) Fibres
● Collagen fibre is most common in animals, is strong and forms tendons.
● Elastic fibre which are long and thin which stretch like rubber bands. Located in
lungs and skin where elasticity are needed.
● Reticular fibre which is short and fine and are located in capillaries which provide
support and bring oxygen to tissues.
, Epithelial Tissue
● Functions include:
protection, absorption, secretion, excretion, filtration, sensory
● Cells are closely packed and hexagonal shaped
● Cell junctions that connect epithelial cells:
They are tight, impermeable and leak-proof
- Desmosome, button like anchors between adjacent membranes which prevent
cells from being pulled apart
- Gap junctions, connected by small cylinder type structures called connexions
which allow communication
● Simple - One layer, where thin surface is needed
● Stratified - Two or more layers, where abrasion is likely
● Squamous - Flattened disc shaped
● Cuboidal - Box like
● Columnar - Tall / Column shaped
● Simple Squamous
Thin and permeable
For lining and covering and a boundary for transport
Located in the alveoli of lungs
● Stratified Squamous
The surface cells are squamous
Keritised - full of keratin and are dead
Non-keratinised - lines the mouth and esophagus
● Simple cuboidal - secretion
● Simple columnar - absorption
● Stratified cuboidal / columnar
Ducts of larger glands such as mammary glands
Pharynx and urethra
● Epidermis of skin is made up of epithelial cells
● Dermis is made up of mainly connective tissue
● Nutrients in skin diffuse from the dermis to epidermis
