1. Types of Membranes There are 4 types of epithelial membranes:
1. Serous Membranes
Line body cavities that do not open to the outside
Reduce friction
Inner lining of thorax and abdomen
Cover organs of thorax and abdomen
Secrete serous fluid
3. Cutaneous Membranes
Covers body
Skin
Types of Membranes
2. Mucous Membranes
Line tubes and organs that open to outside world
Lining of mouth, nose, throat, etc.
Secrete mucus
4. Synovial Membranes
Composed entirely of connective tissue
Lines joints

2. -Connective Tissue -Muscle Tissue -Nervous Tissue

3. Connective Tissue (CT)
Most abundant tissue in body
Composed of cells, fibers, and extracellular matrices
Cells usually divide
Varying degrees of vascularity
Many Functions:
Protection, defense and repair
Insulation (fat storage)
Produce blood cells
Transportation
Binding, support and packaging
Connective Tissue (CT)

4. Connective Tissue Cells
Fibroblasts
Most common
Star-shaped, fixed cell
Secretes protein into matrix producing fibers.
Macrophages
Wandering cells
Act as scavengers (phagocytosis) in injury/infection
Mast Cells
Fixed cells
Release heparin (anticoagulant), and histamine (promotes inflammation).
Connective Tissue Cells

5. Connective Tissue Fibers (Collagenous fibers)
Fibers (produced by fibroblasts)
Collagenous
Thick pieces of protein (collagen).
Inelastic.
Hold structures together.
High tensile strength.
Ligaments, tendons.
Lots of collagenous fibers = Dense CT (white fibers)
Few collagenous fibers = Loose CT
Connective Tissue Fibers (Collagenous fibers)

6. Connective Tissue (Elastic fibers)
Composed of bundles of elastin (elastic protein).
Branching fibers
Not a lot of tensile strength but very flexible
Appear yellow in color.
Found in vocal cords, air passages of respiratory system.
Connective Tissue (Elastic fibers)

7. Connective Tissue (Reticular fibers)
Very thin collagenous fibers that branch to form a supporting network.
Connective Tissue (Reticular fibers)

8. CT cells not adjacent to each other, but have intercellular material (matrix) between them
Matrix is made of cells and consists of gel-like fluids and protein fibers
CT Matrix

9. CT

10. The general categories of connective tissue are: CT Proper
Loose CT
Adipose tissue
Reticular CT
Dense CT
Elastic CT
Specialized CT
Cartilage
Bone
Blood CT

12. Fluid to gel-like matrix Collagenous & elastic fibers
Loose CT:
Mainly fibroblasts
Fluid to gel-like matrix
Collagenous & elastic fibers
Bind skin to structures
Beneath most epithelia
Blood vessels nourish it
Between muscles
Elastic
fiber
(a)
(b)
Collagenous
Fibroblast
Ground
substance

13. Loose CT (Areolar Tissue)
Not very well organized.
It contains fibroblasts, matrix, some fibers scattered about.
It functions to support underlying structures, and helps keep skin bound to the body.
Loose connective tissue is found in the dermis and subcutaneous layers of the skin as well as surrounding muscles.
Sometimes it is called fascia.

14. Adipose CT – made of cells (adipocytes) that contain triglycerides.
The lipid is used to store energy to be used by the body
Adipose tissue is also found around some organs and joints and forms a cushion for shock absorption.
Adipose tissue also insulates the body.
Beneath skin, behind eyeballs, around kidneys and heart
Fat droplet
(a)
(b)
Nucleus
Cell
membrane
Cytsol

15. Lipid
Nucleus of adipocyte
Here is a close up of adipose tissue. You can see the large-filled adipocytes.

16. Adipocytes
Here’s another view of adipose tissue.

17. It supports internal organ walls
Reticular connective tissue consists of a thin supportive network of reticular fibers.
It supports internal organ walls
The walls of the liver, spleen, and lymphatic organs.
CT: Reticular CT
Collagenous
fibers
Fibroblast
White blood
cell
(a)
(b)

18. Reticular connective tissue is web-like and forms a supportive network.

19. Dense (fibrous) CT contains thick collagenous fibers packed together.
It is found in ligaments and tendons (which have a high tensile strength). Dermis of the skin.
Binds body parts together
Dense connective tissue has a poor blood supply
It also contains some elastic fibers, few fibroblasts.
Fibroblasts
Collagenous
fibers
(a)
(b)

20. Dense regular CT Dense irregular CT
Fibers are parallel and dark-staining
Dense irregular CT
Fibers are neither parallel nor dark-staining

21. Elastic connective tissue contains many more elastic fibers than collagenous fibers.
Contains fibroblasts
It is found in attachments between bones like the vertebrae, and in the walls of some hollow internal organs, heart, airways, large arteries.
Elastic fibers
Collagenous
fibers
Fibroblast
(a)
(b)

22. Elastic CT

23. Osseous tissue (bone) has a solid matrix
Functions to support, protect, form blood cells
Attachment point for muscles
Osteocytes (bone cells) are located in lacunae
Canaliculi
Osteocyte in lacuna
Central canal
Lamella
Nucleus
Osteocyte
Cell process in canaliculus
(a)
(b)
Osteon

24. Bone = most rigid CT; hardness comes from mineral salts such as calcium phosphate and calcium carbonate.
It is highly organized into units called osteons.
The primary cell of bone is the osteocyte.
Canaliculi are the canals between the lacunae (small spaces)
Lamellae is the thin plate of bone matrix (rings)

26. Specialized CT: Cartilage
Cartilage is rigid and strong, so it can provide support and protection. It also forms a structural model for developing bones.
Cartilage consists of cells called chondrocytes
Cartilage has no direct blood supply, so nutrients must enter by diffusion.
Specialized CT: Cartilage

27. Hyaline cartilage Cartilage Elastic cartilage Fibrocartilage
Most abundant
Ends of bones
Nose, respiratory passages
Embryonic skeleton
Cartilage
Rigid matrix
Chondrocytes in lacunae
Poor blood supply
Three (3) types:
Hyaline Cartilage
Elastic Cartilage
Fibrocartilage
Elastic cartilage
Flexible
External ear, larynx
Fibrocartilage
Very tough
Shock absorber
Intervertebral discs
Pads of knee and pelvic girdle

28. Specialized CT: Cartilage
Nutrients diffuse into cartilage
The tissue needs water to help move these substances in
As humans age cartilage tends to “dry up” or become dehydrated which lends to degeneration of the tissue.
The cartilage cells or chondrocytes also do not divide very frequently, which contributes to poor healing.
Specialized CT: Cartilage

29. It also has a glassy-appearing matrix.
Chondrocyte
Lacunae
Hyaline cartilage has chondrocytes surrounded by lacunae, as shown above.
It also has a glassy-appearing matrix.
It is found at the ends of bones, the soft part of the nose, larynx and trachea.
Hyaline cartilage serves as a model for bone growth.

30. Another picture of hyaline cartilage.

31. Elastic fibers
Elastic cartilage also has the characteristic chondrocyte in lacuna appearance, along with elastic fibers.
This cartilage is found in the larynx and the ear.

32. Fibrocartilage is characterized by rows of chondrocytes (in lacunae).
It is a very strong cartilage, and is found in the intervertebral discs.

33. Hyaline cartilage Elastic cartilage Chondrocyte Nucleus Extracellular
matrix
(a)
(b)
Lacuna
Elastic cartilage
Chondrocyte
Elastic fibers
Nucleus
Extracellular
matrix
(a)
(b)
Lacuna

34. Fibrocartilage Chondrocyte Nucleus Collagenous fiber Extracellular
matrix
(a)
(b)
Lacuna

35. Blood is also considered a connective tissue
Blood is also considered a connective tissue. It consists of cells suspended in a matrix of fluid called plasma. (RBCs, WBCs, platelets)
It transports gases such as oxygen and carbon dioxide, and functions in clotting and immunity.
Red blood
cells
Plasma
(extracellular
matrix of blood)
Platelets
White blood
cell
(a)
(b)

36. Muscle Tissue Skeletal muscle General characteristics: Smooth muscle
Attached to bones
Striated
Voluntary
General characteristics:
Muscle cells also called muscle fibers
Contractile
Three (3) types:
Skeletal muscle
Smooth muscle
Cardiac muscle
Smooth muscle
Walls of organs
Skin
Walls of blood vessels
Involuntary
Non-striated
Cardiac muscle
Heart wall
Involuntary
Striated
Intercalated discs

37. Skeletal muscle is striated (caused by the density of overlapping protein filaments called actin and myosin).
Voluntary – we can control this
It moves the muscles
Located on muscles usually attached to bones
Multinucleate – contain multiple nuclei per cell

38. Cardiac muscle is also striated, but has a unique structure called an intercalated disc.
The disks are special intercellular junctions that allow electrochemical impulses to be conveyed across the tissue.
Found only in heart, and its main function is to allow the heart to beat.
Involuntary – because we cannot control this
Uninucleate – contain only one nucleus per cell

39. Skeletal Muscle Cardiac Muscle Striations Nucleus Intercalated disc
Portion of a
muscle fiber
Nuclei
(a)
(b)
Cardiac Muscle
Intercalated
disc
Nucleus
Striations
(a)
(b)

40. Smooth muscle is involuntary – we cannot control this
Nucleus
Cytoplasm
(a)
(b)
Smooth muscle is involuntary – we cannot control this
It is non-striated because the myofilaments are not as dense as in cardiac and skeletal muscle.
Smooth muscle is found in organs such as in the gastrointestinal system and the arteries.
Smooth muscle function is to regulate all internal organs’ movements, like stomach, liver, kidneys.
Uninucleate – contain only one nucleus per cell

41. Nervous tissue consists of nervous system cells called neurons, and supportive cells called glia (they bind & support nervous tissue).
Nervous tissue function is sensory reception and conduction of nerve impulses
Found in brain, spinal cord, peripheral nerves
Nervous Tissue
Cell
membrane
Neuroglial
cells
Cytoplasm
Cellular
process
Nucleus
(a)
(b)

42. Nervous tissue contains neurons and glial cells.
Neuron has a main cell body called a soma
Neuron has dendrites that receive messages and a long axon that sends messages