Classification of Connective Tissues
Embryonic connective tissues
1. Mesenchymal
2. Mucous
Connective tissue proper
1. Loose (areolar)
2. Dense
a. Dense irregular
b. Dense regular
-collagenous
-elastic
Specialized connective tissue
1. Cartilage
2. Bone
3. Blood
4. Adipose
-involved in energy storage, insulation, cushioning of organs and
secretion of hormones
-Large cells, can be up to ~100um
-Lipid mass is not membrane bound
-White (unilocular) or brown (multilocular)
Hormones involved in short-term weight control
ghrelin – stimulates appetite
Peptide YY – induces sense of fullness
Hormones involved in long-term weight control
leptin – produced exclusively by adipocytes.
-generally thought to reduce appetite (obese people have
high levels and are thought to be resistant to leptin action)
insulin – enhances conversion of glucose into triglycerides
-volume of cells and
plasma is ~45 and 55%
respectively
-Hematocrit - volume of
packed erythrocytes in a
sample of blood
Normal hematocrit
~39-50% in males
~35-45% in females
Leukocytes and platelets
constitute only ~1% of
blood volume
a
CARTILAGE
c
Specialized connective tissue, part of skeletal
system
d
Functions: provide flexible support (bone rigid
template for bone formation
b
Locations: limited sites – respiratory system,
joints, external ear
Composition: cells + matrix (properties from
matrix)
1. Matrix: a. Fibers: collagen II, elastic fibers
b. Ground substance: proteoglycans
and glycosaminoglycans (GAGs)
2. Cells: chondroblasts, chondrocytes,
c
FEATURES OF
CARTILAGE
Perichondrium
•Avascular
•No nerves
•No lymphatics
Isogenous
group
Territorial matrix
around
chondrocytes
Chondrocyte in lacuna
Interterritorial matrix between
isogenous groups or single
cells.
•CARTILAGE IS A SHOCK ABSORBER
•Add pressure: water forced out of tissue, absorbs
pressure
•Release pressure: water rebinds PG aggregate and tissue
returns to original size
TYPES OF CARTILAGE
1. Hyaline: most common – nasal septum, joint surface,
ribs
2. Elastic: enriched with elastic fibers – ear, larynx
-Looks like hyaline cartilage with the addition of elastic fibers
between cells
3. Fibrocartilage: found in interverterbral disks,
tendon/ligament attachment.
-See rows of chondrocytes with increased fibrous matrix
between between them
Hyaline Cartilage
Elastic Cartilage
Fibrocartilage
FUNCTIONS OF BONE
1. Support
2. Protection (skull)
3. Locomotion
4. Calcium store (also Mg and Na)
5. Hematopoiesis (marrow)
TYPES OF MATURE BONE
Cancellous (spongy): fine irregular plates – trabeculae
inside long bones (marrow)
gives strength without weight
Compact: highly ordered
Types: outer and inner circumferential lamellae
-contains Haversian systems (osteons)
COMPOSITION OF BONE: cells + matrix
Matrix
1. Organic a) fibers: type I collagen, highly organized
b) ground substance: little, some PG as
cartilage
2. Inorganic: Calcium phosphate complexes forms 50%
of the matrix, giving the material its rigidity
***Bone looks solid but is alive, dynamic and continually
remodeling.
***Is highly vascularized (compared to cartilage)
PRIMARY CELLS IN BONE
1. Osteoblasts: immature, synthesize and secrete
osteoid, which becomes mineralized to give bone; do
not divide.
2. Osteocytes: surrounded by matrix, maintain matrix; do
not divide.
3. Osteoclasts: large multinucleate cells, resemble
macrophage in function, remodel bone by resorbing
bone matrix.
Main cells include:
-Osteoblast
-Osteocyte
-Osteoclast
Articular cartilage
EPIPHYSIS
DIAPHYSIS
EPIPHYSIS
Cancellous bone
Compact bone
Periosteum
Marrow cavity
Compact (Ground) Bone
Muscle Tissue
Structure of Skeletal Muscle Tissue
EM of Striated Muscle
The Sarcomere –extends from Z-line to Z-line
-the smallest repetitive subunit of the contractile unit
Arrangement of Thick and Thin Filaments
Sarcomeres
at different
functional
stages
Neuromuscular Junction
Cardiac Muscle Tissue
Smooth
Muscle
Tissue
Nerve Tissue
ORGANIZATION
OF NERVOUS
SYSTEM
Peripheral Nervous System
Can be divided into:
-the somatic nervous system
-the autonomic nervous system
-sympathetic division
-parasympatheic division
-enteric division
Components include:
-cranial nerves
-spinal nerves
-peripheral nerves
-ganglia
-somatic or sensory - dorsal root ganglia
-autonomic sympathetic, parasympathetic, enteric
-specialized nerve endings
Types of
Neurons
Can be classified
based on:
-morphology
-function
-neurotransmitters
Organization
of a
Typical Neuron
Nerve Organization
From Junqueira and Carneiro. McGraw-Hill Publishing, 2005
From Junqueira and Carneiro. McGraw-Hill Publishing, 2005