Test II: Connective Tissue Flashcards
Characteristics of Connective Tissue
- Specialized cells
- Solid extracellular protein fibers
- Fluid extracellular ground substance
The Extracellular Components of Connective
Tissue (Fibers and Ground Substance)
– Make up the matrix
• Majority of tissue volume
• Determines specialized function
Functions of Connective Tissue
– Establishing a structural framework for the body
– Transporting fluids and dissolved materials
– Protecting delicate organs
– Supporting, surrounding, and interconnecting
other types of tissue
– Storing energy reserves, especially in the form of
triglycerides
– Defending the body from invading
microorganisms
Classification of Connective Tissues
1. Connective tissue proper • Connect and protect 2. Fluid connective tissues • Transport 3. Supporting connective tissues • Structural strength
The most abundant connective cell type
• Found in all connective tissue proper
• Secrete proteins and hyaluronan (cellular cement)
Fibroblasts
The second most abundant cell type
• Found in all connective tissue proper
• Maintain the fibers of connective tissue proper
Fibrocytes
Fat cells • Each cell stores a single, large fat droplet do not divide (hypertrophy only) – Expand to store fat – Shrink as fats are released
Adipocytes
Stem cells that respond to injury or infection
• Differentiate into fibroblasts, macrophages, etc.
divide and differentiate (hyperplasia)
– To produce more fat cells
– When more storage is needed
Mesenchymal Cells
Large, amoeba-like cells of the immune
system
• Eat pathogens and damaged cells
Macrophages
• Fixed macrophages stay in tissue
• Free macrophages migrate
Stimulate inflammation after injury or infection
• Release histamine and heparin
Mast Cells
leukocytes (white blood cells)
that also contain histamine and heparin
Basophils
Specialized immune cells in lymphatic
(lymphoid) system
Lymphocytes
For example, lymphocytes may develop into plasma cells (plasmocytes) that produce antibodies
Phagocytic blood cells
• Respond to signals from macrophages and mast
cells
• For example, neutrophils and eosinophils
Microphages
Synthesize and store the brown pigment
melanin
Melanocytes
2 types of adipose tissue
- White fat
2. Brown fat
Type of fat that is – Most common – Stores fat – Absorbs shocks – Slows heat loss (insulation)
White fat
Type of fat that is
– More vascularized
– Adipocytes have many mitochondria
– When stimulated by nervous system, fat breakdown
accelerates, releasing energy
– Absorbs energy from surrounding tissues
Brown fat
Functions of adipose tissue
Provides padding and cushions shocks; insulates
(reduces heat loss); stores energy
Tightly packed, parallel collagen fibers
Dense Regular Connective Tissue
Types of Dense Regular Connective Tissue
tendons
ligaments
aponeuroses
attach muscles to bones
Tendons
connect bone to bone and stabilize
organs
Ligaments
attach in sheets to large, flat
muscles
Aponeuroses
Functions of dense regular connective tissue
Provides firm attachment; conducts pull of muscles; reduces friction between muscles; stabilizes relative positions of bones
– Interwoven networks of collagen fibers • Layered in skin • Around cartilages (perichondrium) • Around bones (periosteum) • Form capsules around some organs (e.g., liver, kidneys)
Dense Irregular Connective Tissue
Functions of Dense Irregular Connective Tissue
Provides strength to resist forces applied from many
directions; helps prevent overexpansion
of organs such as the urinary bladder
Locations of dense, irregular connective tissue
Capsules of visceral organs; periostea
and perichondria; nerve and muscle sheaths; dermis
Fluid Connective Tissues
– Blood and lymph
– Watery matrix of dissolved proteins
– Carry specific cell types (formed elements)
Fluid Elements of Connective Tissues
– Extracellular
• Plasma
• Interstitial fluid
• Lymph
are responsible for the transport of oxygen
(and, to a lesser degree, of carbon dioxide) in the blood.
RBC’s
help defend the body from infection and disease.
White blood cells, or leukocytes
membrane-enclosed packets of cytoplasm that function in blood clotting; These cell fragments are involved in the clotting response that seals leaks in damaged or broken blood vessels.
Platelets
Extracellular fluid • Collected from interstitial space • Monitored by immune system • Transported by lymphatic (lymphoid) system • Returned to venous system
Lymph
Supporting Connective Tissues
Bone and cartilage
- Gel-type ground substance
* For shock absorption and protection
Cartilage
- Calcified (made rigid by calcium salts, minerals)
* For weight support
Bone
Bone contains four types of cells
- Osteocytes
- Osteoblasts
- Osteoprogenitor cells
- Osteoclasts
– Mature bone cells that maintain the bone matrix
– Are between layers (lamellae) of matrix
– Connect by cytoplasmic extensions through
canaliculi in lamellae
– Do not divide
Osteocytes
Two major functions of osteocytes
- To maintain protein and mineral content of matrix
2. To help repair damaged bone
– Immature bone cells that secrete matrix
compounds (osteogenesis)
Osteoblasts (Osteoblasts surrounded by bone become osteocytes)
matrix produced by osteoblasts,
but not yet calcified to form bone
Osteoid
– Mesenchymal stem cells that divide to produce osteoblasts – Located in endosteum, the inner cellular layer of periosteum – Assist in fracture repair
Osteoprogenitor Cells
– Secrete acids and protein-digesting enzymes
– Giant, multinucleate cells
– Dissolve bone matrix and release stored
minerals (osteolysis)
– Derived from stem cells that produce
macrophages
Osteoclasts
The Structure of Spongy Bone
– The matrix forms an open network of trabeculae
– Trabeculae have no blood vessels
– The space between trabeculae is filled with red bone marrow
Red bone marrow
- Which has blood vessels
- Forms red blood cells
- And supplies nutrients to osteocytes
Yellow bone marrow
• In some bones, spongy bone holds yellow bone
marrow
• Is yellow because it stores fat
Bone Development
– Human bones grow until about age 25
Bone formation
Osteogenesis
The process of replacing other tissues with bone
Ossification
The process of depositing calcium salts
Calcification
Epiphyseal Lines
– When long bone stops growing, after puberty:
• Epiphyseal cartilage disappears
• Is visible on X-rays as an epiphyseal line
Mature Bones
As long bone matures:
• Osteoclasts enlarge medullary (marrow) cavity
• Osteons (compact bone) form around blood
vessels
Process of Remodeling
– The adult skeleton: • Maintains itself – Replaces mineral reserves • Recycles and renews bone matrix • Involves osteocytes, osteoblasts, and osteoclasts
Effects of Exercise on Bone
Mineral recycling allows bones to adapt to stress
– Heavily stressed bones become thicker and
stronger
Bone Degeneration
– Bone degenerates quickly
– Up to one third of bone mass can be lost in a few
weeks of inactivity
Hormone Calcitriol
• Made in the kidneys
• Helps absorb calcium and phosphorus from
digestive tract
• Synthesis requires vitamin D3 (cholecalciferol)
Hormone that stimulates bone growth
Growth hormone and thyroxine
Hormone that stimulates osteoblasts
Estrogens and androgens
Hormone that regulates calcium and phosphate levels
Calcitonin and parathyroid hormone
Calcitonin and Parathyroid Hormone
Control
– Affect: 1. Bones – Where calcium is stored 2. Digestive tract – Where calcium is absorbed 3. Kidneys – Where calcium is excreted
Know responses when calcium levels are low or high
Slides
