Introduction to Human Tissues #3

Laura Fraser Cotlin, Ph.D.

Fundamentals 2 – Dental/Optometry

November 2, 2011

Classification of Connective Tissues

Embryonic connective tissues1. Mesenchymal

2. Mucous

Connective tissue proper1. Loose (areolar)2. Dense

a. Dense irregularb. Dense regular

-collagenous-elastic

Specialized connective tissue1. Cartilage2. Bone3. Blood4. Adipose

Adipose Tissue

Adipocytes

-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 controlghrelin – stimulates appetitePeptide YY – induces sense of fullness

Hormones involved in long-term weight controlleptin – 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

Fat absorption and release

White Adipose Tissue

Blood

The hematocrit of human blood

-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

Composition of Whole Blood

Fluid is called PLASMA occupies ~55% of the total blood volume liquid extracellular material

Plasma that lacks coagulation (clotting factors) is called SERUM.

Cartilage

CARTILAGE Specialized connective tissue, part of skeletal

system

Functions: provide flexible support (bone rigid template for bone formation

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

b

d

c

a

FEATURES OF CARTILAGE

• 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

• Avascular

• No nerves

• No lymphatics

Perichondrium

Isogenous group Chondrocyte in lacuna

Territorial matrix around chondrocytes

Interterritorial matrix between isogenous groups or single cells.

Chondrocytes in association with

Matrix

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

Bone Tissue

FUNCTIONS OF BONE1. Support2. Protection (skull)3. Locomotion4. Calcium store (also Mg and Na)5. Hematopoiesis (marrow)

TYPES OF MATURE BONECancellous (spongy): fine irregular plates – trabeculae

inside long bones (marrow) gives strength without

weight

Compact: highly orderedTypes: outer and inner circumferential lamellae-contains Haversian systems (osteons)

COMPOSITION OF BONE: cells + matrixMatrix

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 BONE1. 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

Bone Cells

EPIPHYSIS

DIAPHYSIS

EPIPHYSIS

Articular cartilage

Cancellous bone Compact bone

PeriosteumMarrow cavity

Compact (Ground) Bone

Spongy Bone

(intermembrane

ous)

Muscle Tissue

Types of Muscle Tissue

Common Features of ALL MUSCLE TISSUE

Derived from mesoderm layer

Cell membrane = sarcolemma

Cytoplasm = sarcoplasm

ER = sarcoplasmic reticulum (SR)

Contraction of all muscle depends on the interaction of actin and myosin

Contraction of all muscle is regulated by cellular calcium

Skeletal Muscle Tissue

bundles of very long, cylindrical multinucleated cells showing cross striations.

contraction is quick, forceful --> caused by interactions of thin actin filaments and thick myosin filaments.

Cell size: length can be up to ~3cm

diameter ranges 10-100um

Associated Connective Tissue Epimysium - dense connective tissue surrounding the entire

muscle. Perimysium - connective tissue surrounding the bundles of

fibers within a muscle. Endomysium – basement membrane and delicate connective tissue

surrounding each muscle fiber

Structure of Skeletal Muscle Tissue

Long. section of Skeletal Muscle

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

Cardiac Muscle Tissue heart muscle consists of tightly knit bundles of cells which

provide for a characteristic wave of contraction that leads to a wringing out of the heart ventricles.

exhibit a cross-striated banding pattern identical to that of skeletal muscle.

structure and function of the contractile proteins are almost the same as in skeletal muscle.

distinguishing characteristic is the presence of intercalated disks - dark-staining transverse lines that cross the chains of cardiac cells at irregular intervals.

EM of cardiac muscle tissue

Structure of the Intercalated Disk

Long. section of Cardiac Muscle

Smooth Muscle Tissue

Smooth Muscle Tissue

composed of elongated, nonstriated cells

Cells are enclosed by a basal lamina and network of reticular fibers these 2 components serve to combine the forces generated by each

smooth muscle fiber into a concerted action.

cells are fusiform (largest at midpoint and tapered at the ends) with a single centrally-located nucleus

tight packaging of tissue is achieved by lining up cells with the narrow parts of some cells against the broad parts of neighboring cells.

the cell boarders become scalloped when contracted, and the nucleus becomes folded or has a cork-screw appearance.

Smooth Muscle Tissue

composed of elongated, nonstriated, fusiform cells(largest at midpoint and tapered at the ends)

tight packaging of tissue is achieved by lining up cells with the narrow parts of some cells against the broad parts of neighboring cells.

Contain dense bodies for attachment of filaments and propagation of contraction.

Nerve Tissue

ORGANIZATION OF 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

Peripheral Nervous System

Types of Neurons

Can be classified based on:

-morphology-function-neurotransmitters

Organization of a

Typical Neuron

From Junqueira and Carneiro. McGraw-Hill Publishing, 2005

Nerve Organization

From Junqueira and Carneiro. McGraw-Hill Publishing, 2005