BIO 121 – Molecular Cell Biology
Lecture Section IV
A. Cells in the Context of Tissue,
Organ and Organismal Architecture
B. Wound Healing
Four Types of Vertebrate Tissue
1.Epithelium
2.Connective Tissue
3.Muscle
4.Nervous Tissue
1. Architecture of Epithelium
• Simple, Stratified, Pseudostratified, Transitional
• Squamous, Cuboidal, Columnar
• Ciliated or not
• Examples:
–
–
–
–
Small Intestine = Simple Columnar Epithelium
Trachea = Ciliated Pseudostratified Columnar Epithelium
Blood Vessel = Simple Squamous Epithelium
Skin = Stratified Squamous Epithelium
Structure equals Function
– Small Intestine:
Simple Columnar Epithelium = absorption
– Trachea:
Ciliated Pseudostratified Columnar Epithelium = filtering debris
– Blood Vessel:
Simple Squamous Epithelium = gas exchange
– Skin:
Stratified Squamous Epithelium = protective physical barrier
Simple,
Columnar
Epithelium
Function:
1. absorption of nutrients
2. enzymatic digestion at neutral pH
3. multiple defensive mechanisms
4 Cell types in Small Intestine
Small Intestine
Cellular Adhesion in Small Intestine
Desmosomes
Hemidesmosomes
Adherens Junctions
Occluding Junctions
Tracheal Epithelium
Ciliated Pseudostratified
Columnar Epithelium
with Goblet Cells
1. Mucus traps dust and airborne microorganisms
2. Ciliar waving gets rid of
unwanted material
The Vasculature: Simple, Squamous Epithelium
Gas Exchange
Fluid Exchenge
Epidermis of Skin
Stratified
Squamous
Epithelium
Creates tough,
waterproof
barrier
Differentiation and Direction of Movement in Epidermis
Cornification
is the overproduction of
cytokeratins,
ECM and the
adhesions to
a degree that
stops cellular
metabolism.
2. Mesenchymal Cell Types and
Connective Tissues
Figure 23-52 Molecular Biology of the Cell (© Garland Science 2008)
The Fibroblast
Loose Connective Tissue
Dense Regular CT
Dense Irregular CT
Elastic Connective Tissue
The dermis is as complex
as the epidermis and
contributes greatly to
skin function
Cartilage and the Chondrocyte
Lacunar Structure of the Hyaline Cartilage
Extremely low blood flow
Osteoblasts
Lacunar structure of the long bones
Cortical Bone vs. Spongy Bone
Cell Types of the Bone
Marrow of
Long Bones
has Stem Cells
Start out as cartilage models built by chondrocytes
Chondrocytes hypertrophy, calcify and die
Osteoblasts and osteoclasts finish up
The Adipocyte
Mesenchymal
Stem Cells are a
continuous source
of adipocytes
3. Contractile Tissue
Figure 23-47a Molecular Biology of the Cell (© Garland Science 2008)
Arteries, veins
Lymphatic vessels
Gastrointestinal tract
Respiratory tract
Urinary bladder
Reproductive tract
Urinary tract
Iris of the eye
Erector pili of skin
4. Nervous Tissue
Nerve Bundles
Cutaneous Wound Healing
The skin is a complex organ...
Many cells and activities involved
Many cells and activities involved in Healing
Clotting
Scarring
Re-establishing
Function
• Four overlapping stages to wound healing
– Hemostasis
– Inflammation
– Proliferation
– Maturation
Blood flows into the exposed ECM of
the injured tissue.
RBC and Platelets Trapped in Fibrin Clot
Clotting factor
VII from the
blood contacts
tissue factor on
cells in the
damaged
tissues to
activate clotting
Platelet activation in the. clot makes them sticky
and releases their signal storage vesicles
©2000 by Lippincott Williams & Wilkins
Camacho A , Dimsdale J E Psychosom Med 2000;62:326-336
Positive feedback
activates even more
Platelet activation
releases growth
factors by regulated
secretion
Inflammation is a process mediated primarily
by WBC as part of our innate immunity
- Resident mast cells and macrophages
- Recruited monocytes and neutrophils
Resident mast cells also degranulate
rubor = redness
calor = heat
tumor = swelling
dolor = pain
Activated mast cell activities
Figure 1 Development and differentiation of macrophages.
Rickard A J , Young M J J Mol Endocrinol 2009;42:449-459
© 2011 Society for Endocrinology
Activated macrophage activities
Neutrophil Diapedesis
Activated neutrophils are phagocytic
Proliferation re-establishes tissue function
• Reconnection of
the dermal
connective tissue
• Integrity of the
epidermal layers
• Re-establishment
of blood flow
Reconnection of
the dermal CT
Cell Migration or “Crawling”
• The Basic Mechanism
–
–
–
–
Triggered by signals from outside the cell
Actin-myosin based movement
Requires attachments to outside to pull against
Gotta’ drag all of the cell contents along for the ride
Chemotaxis
Circumferential receptors
Rho-family GTPases (monomeric)
Rho-dependent kinases
1. Actin monomer nucleotide exchange
2. Actin fiber polymerization and disassembly
3. Myosin motor ATPase activity
Figure 17-62 (part 1 of 3) Molecular Biology of the Cell (© Garland Science 2008)
Formation of the scar matrix
1.
2.
3.
4.
glycosaminoglycans
proteoglycans
fibrous proteins
elastic proteins
Re-establishment of the
epidermal epithelium
involves both mitosis and
epithelial migration
Also must reform the basal lamina
Re-epithelialization below the scab
scar
Fi
Model depicting α3β1-integrin-mediated functions of epidermis that contribute to wound
healing.
Mitchell K et al. J Cell Sci 2009;122:1778-1787
©2009 by The Company of Biologists Ltd
Figure 23-34 Molecular Biology of the Cell (© Garland Science 2008)
Maturation Phase
Wound contraction by myofibroblasts
Stitches Perform Wound Contracture
Collagen Remodeling
A scar never reaches the strength of
undamaged tissue
Healing Abnormalities
• Failure to heal: Excessive Inflammation
• Excessive scarring: Wound Fibrosis
– Hypertrophic Scarring
– Keloid Scarring
Biofilms May Block Healing
Hypertrophic scars result from failed
fibroblast contracture
Don’t extend beyond the original wound edge
Keloid scars result from excessive
TGF-b receptors on fibroblasts
Extend to fibroblasts outside the wound
People have
exploited these
conditions to create
the ‘keloid tattoo’