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Bone can be divided into two types: compact and spongy. Compact bone is found in the shaft (or diaphysis) of a long bone and the surface of the flat bones, while spongy bone is found in the end (or epiphysis) of a long bone. Compact bone is organized into subunits called osteons , as illustrated in [link] . A blood vessel and a nerve are found in the center of the structure within the Haversian canal, with radiating circles of lacunae around it known as lamellae. The wavy lines seen between the lacunae are microchannels called canaliculi ; they connect the lacunae to aid diffusion between the cells. Spongy bone is made of tiny plates called trabeculae these plates serve as struts to give the spongy bone strength. Over time, these plates can break causing the bone to become less resilient. Bone tissue forms the internal skeleton of vertebrate animals, providing structure to the animal and points of attachment for tendons.

 Illustration A shows a cross section of a long bone with wide protrusions at either end. The outer part is compact bone. Inside the compact bone is porous spongy bone made of web-like trabreculae. The spongy bone fills the wide part at either end of the bone. In the middle, a hollow exists inside the spongy bone. Illustration B shows several circular osteons clustered together in compact bone. At the hub of each osteon is an opening called the Haversian canal filled with blood and lymph vessels and nerves. The lamellae surrounding the Haversian canal resemble tree rings.  Lacunae are wide spaces in the rings between the lamellae. Microchannels called canaliculi radiate through the rings out from the central Haversian canal, connecting the lacunae together. Illustration C shows small osteoclasts surrounding the outside of bone. Larger osteoclasts are also on the outer surface, forming a hollow in the bone. Osteocytes are long, thin cells in the lacunae.
(a) Compact bone is a dense matrix on the outer surface of bone. Spongy bone, inside the compact bone, is porous with web-like trabeculae. (b) Compact bone is organized into rings called osteons. Blood vessels, nerves, and lymphatic vessels are found in the central Haversian canal. Rings of lamellae surround the Haversian canal. Between the lamellae are cavities called lacunae. Canaliculi are microchannels connecting the lacunae together. (c) Osteoblasts surround the exterior of the bone. Osteoclasts bore tunnels into the bone and osteocytes are found in the lacunae.

Adipose tissue

Adipose tissue, or fat tissue, is considered a connective tissue even though it does not have fibroblasts or a real matrix and only has a few fibers. Adipose tissue is made up of cells called adipocytes that collect and store fat in the form of triglycerides, for energy metabolism. Adipose tissues additionally serve as insulation to help maintain body temperatures, allowing animals to be endothermic, and they function as cushioning against damage to body organs. Under a microscope, adipose tissue cells appear empty due to the extraction of fat during the processing of the material for viewing, as seen in [link] . The thin lines in the image are the cell membranes, and the nuclei are the small, black dots at the edges of the cells.

Illustration shows irregularly shaped cells with tiny nuclei clustered next to the cell’s outer membrane.
Adipose is a connective tissue is made up of cells called adipocytes. Adipocytes have small nuclei localized at the cell edge.


Blood is considered a connective tissue because it has a matrix, as shown in [link] . The living cell types are red blood cells (RBC), also called erythrocytes, and white blood cells (WBC), also called leukocytes. The fluid portion of whole blood, its matrix, is commonly called plasma.

Different types of blood cells are shown. Red blood cells are disc-shaped, with a central indentation. Platelets are much smaller than red blood cells, narrow and long. Neutrophils, eosinophils, lymphocytes, monocytes and basophils are all about three times the diameter of a red blood cell and round. They differ in the shape of the nucleus, and in the presence or absence of granules in the cytoplasm. Macrophages, which are the largest cell type, have pseudopods which give them an irregular shape.
Blood is a connective tissue that has a fluid matrix, called plasma, and no fibers. Erythrocytes (red blood cells), the predominant cell type, are involved in the transport of oxygen and carbon dioxide. Also present are various leukocytes (white blood cells) involved in immune response.

The cell found in greatest abundance in blood is the erythrocyte. Erythrocytes are counted in millions in a blood sample: the average number of red blood cells in primates is 4.7 to 5.5 million cells per microliter. Erythrocytes are consistently the same size in a species, but vary in size between species. For example, the average diameter of a primate red blood cell is 7.5 µl, a dog is close at 7.0 µl, but a cat’s RBC diameter is 5.9 µl. Sheep erythrocytes are even smaller at 4.6 µl. Mammalian erythrocytes lose their nuclei and mitochondria when they are released from the bone marrow where they are made. Fish, amphibian, and avian red blood cells maintain their nuclei and mitochondria throughout the cell’s life. The principal job of an erythrocyte is to carry and deliver oxygen to the tissues.

Questions & Answers

which element is the largest
Haja Reply
how many groups do we have in the periodic table
Theola Reply
seven groups
the one that makes eight is the noble gases
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Smart Reply
nearly a hundred million
what do you by one?
two times
just only one time
what is a function of cell sap
it repair worn out tissue
when is the right time for playing sex to prevent pregnancy?
what is biology
Darkoa Reply
it's study of all living organisms and their characteristics
by what proces do ameaba reproduce?
Okello Reply
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what is biology
amoeba reproduce asexually
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Mary Reply
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what is active transport
Amona Reply
is the movement's of water & mineral salts from the reason of highly concentrated to the reason of low concentration across semi permeable membrane & it take place in plant
in what situation would the use of a scanning microscope be ideal and why?
Anthony Reply
what is euglina
Ruth Reply
no idea
Euglena is a unicellular organism that has both animal- like and plant- like features.
define hybridization?
Which of the following statements regarding membrane transport is false? 1. Glucose is transported only by facilitated diffusion 2.Each protein carrier will only bind and b transport one type of solute.
#2. Each protein carrier will only bind and b transport one type of soluble
#2 is false for the regarding membrane transport.
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what is gene
Okello Reply
what is somatic cell
garaadmaxamed Reply
what is Biology?
is the study of living things
what is organ
what is biology
Isiaka Reply
is the study of all living things
and their interactions with each other and the environment
it is the study of all living organisms and their characteristics
the study of living things and their surroundings
what's is biology
Mohamed Reply
what's is dna
deoxybonucliec acid
explain the osomor regulations in amoeba and paramecium
Adannaya Reply
explain the osimoregulation in man
who can explain the osmoregulation in amoeba and in man

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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