Glands and Connective tissue

Question 1

Describe how to classify glands based on whether they are simple or compound

Answer 1

Simple duct structures, do not have branching at the ducts, whilst compound cut structures are where the ducts branch off into other ducts

Question 2

Describe how to classify glands based on whether they are acinar or tubular

Answer 2

Acinar secretory structures have a circular branching, (branching looks like a circle), whilst tubular structures have a straight like branching.

Question 3

Describe how to classify glands on whether or not they produce mucous or serous secretions

Answer 3

Glands that produce mucous secretions appear pale after bleaching as the fat is removed when the structure is fixed, unlike serous which stains.

Question 4

How do the unicellular glands (goblet cells) in the jejunum and colon relate to their function

Answer 4

Goblet cells line the surface of the epithelium. They stain with sugars so if a different staining is used, there will be no staining, but if a sugar stain is used, it will appear magenta.
Goblet cells are unicellular intraepithelial mucin-secreting glands. Their role is to protect the surface of epithelium, lubricate it, and catch harmful particles.

Question 5

What is the main difference between mucous and serous glands

Answer 5

The main difference between serous and mucous is that serous gland secretes a thin, watery secretion containing zymogens, antibodies, and inorganic ions, which are mainly involved in digestion and defence whereas mucous gland secretes a thick, viscous secretion, containing mucin, which is mainly involved in lubrication.

Question 6

How do goblet cells work

Answer 6

Goblet cells secrete mucus – mucous glands
Their product is packed in vesicles inside the cell, and released by exocytosis – merocrine glands
They release their product on the surface of epithelium rather than in blood – exocrine glands.
Goblet cells are mostly found scattered in the epithelia of the small intestines and respiratory tract. The morphology of goblet cells reflects their function, with the cell containing all the organelles necessary for the production of glycosylated proteins called mucins.

Question 7

Discuss the anatomical location of the Parotid glands and how it relates to its function

Answer 7

The Parotid is one of a pair of salivary glands situated below and in front of each ear, (you can palpitate it on your jawline). It is almost entirely serous exocrine gland of the acinar type, and they occur in pairs.
Each parotid is a compound gland. Its enzyme secretion is stored in the apical cytoplasm of acinar cells as zymogen granules. Parotid glands produce saliva (even though it’s the largest of the salivary glands, it only produces around 30%).

Question 8

What is the purpose of the striated duct in the Parotid gland

Answer 8

The striated duct connects the intercalated duct and the interlobular duct.

Question 9

What is the anatomical location of the Submandibular glands and what is their function

Answer 9

The Submandibular glands is one of 3 salivary glands and is found on the floor of your mouth below the lower jaw. It is a compound, tubuloacinar mixed gland with serous (granular) and mucous (pale-staining) and mixed acini all being present in the same tissue.
It produces saliva, and unstimulated, produces the most saliva of the 3 glands, (produces 60%).

Question 10

How do the ducts in the Parotid/Submandibular combine

Answer 10

The tubules leading from the acini also contain flattened, small, myoepithelial cells. These cells are responsible for the contractile activity of the ducts as they express the stored saliva. Smaller ducts are known as intralobular ducts, and they drain into the intercalated ducts. The walls of the intercalated ducts contain cuboidal epithelial cells. Intercalated ducts then unite to form striated ducts, which contain columnar cells in the walls and highly folded basolateral membranes.
Finally, ducts arising from each lobule combine to form excretory ducts. The walls of these larger conduits contain more connective tissue, and an atypical arrangement of simple columnar or cuboidal, stratified columnar or cuboidal, or pseudostratified epithelia.

Question 11

What is the anatomical location of the liver and its function.

Answer 11

The liver is the largest exocrine gland, and it has a lot of functions including:
- Hepatic blood Supply
- Protein synthesis
- Carbohydrate and Liver metabolism
- Detoxification

Question 12

Explain the Hepatic blood supply

Answer 12

Liver is composed of millions of specialised exocrine cells called hepatocytes. When entering liver lobule, deoxygenated blood from hepatic portal vein mixes with oxygenated blood from hepatic artery and passes across the surface of hepatocytes, which are arranged in a 33-dimensional wall.
As the blood passes across the fenestrated endothelial cells, large molecules gain access to hepatocytes that contain numerous different membrane transport proteins that facilitate transport of molecules across plasmalemma. Molecules not absorbed this way pass through central hepatic vein, back to circulation. P450 cytochrome enzymes transform many molecules and transport them into the bile canals and blood.
Kuppfer cells, Stella the cells, and dendritic cells prevent microbial interaction with the hepatic cells by acting as resident APCs.

Question 13

Explain the function of the liver in terms of storage

Answer 13

• Stores metals such as iron and copper
• Stores lipid soluble vitamins (A, D, E, K)
• Stores sugars such as glucose (as glycogen)

Question 14

Explain the function of the liver in terms of Anabolism (production)

Answer 14

It produces more than 60% of the body’s proteins such as:
- Major plasma proteins like Albumin
- Enzymes like catalase and coagulation factors
- Lipid carrier proteins like Apolipoproteins (HDL, LDL)
Amino acid synthesis such as glutamate, glutamine etc.
Haemopoiesis in the embryo/foetus

Question 15

Explain the function of the liver in terms of catabolism (destruction)

Answer 15

• Breakdown of drugs
• Hormones such as steroids, insulin, glucagon, etc.
• Haemoglobin as Bilirubin is passed to the gull bladder
• Poisons/toxins
• Sugars

Question 16

Explain Kupffer cells

Answer 16

Kupffer cells are specialist macrophages that form part of the sinusoidal lining and are constantly exposed to gut-derived bacteria, microbial debris, cell debris and bacterial endotoxins. They have 2 functions:
- To remove any bacteria, present in the sinusoidal lumen.
- To destroy damages erythrocytes (120-day old red blood cells) and thus aid in the recycling of haemoglobin

Question 17

Explain Stellate (Ito) cells

Answer 17

In the normal liver, they are in a quiescent state,, and represent 5-8% of total liver cells. Each cell has long protrusions that extend from the cell body and wrap around the sinusoids
The lipid droplets store vitamin A. The function of the quiescent cells is unclear but some things k they have a role as a live APC.
When the liver is damaged, Stella the cells change to an active state,, which is shown by proliferation, contractility and chemo taxis of immune cells. The state of stellar cell is the main source of extra cellular matrix production in liver injury which is a factor in vitamin A deficiency and the secretion of collagen scar tissue which causes liver cirrhosis and hepatocarcinoma.

Question 18

Explain Hepatocytes

Answer 18

Hepatocytes constitute 80% of liver cell population. They have a remarkable regenerative ability and compared to other cells they have:
- numerous mitochondria
- lots of peroxisomes
- Numerous free ribosomes
- Lots of RER and SER and Golgi apparatipus
Their functions include:
- Protein synthesis and storage
- Carbohydrate metabolism and storage
- Fat metabolism and Storage
- Cholesterol metabolism, synthesis of phospholipid and bile salts.
- Detoxification, modification and excretion of exogenous and endogenous substances
- Initiation of formation and secretion of bile
- The storage of essential vitamins and minerals

Question 19

What are other functions of the liver (unrelated to storage, anabolism or catabolism)

Answer 19

• Used for bile production (main exocrine function).
• Used for filtering of cell debris from blood
• Hormones/Growth factors (endocrine) such as Angiotensinogen, Thrombopoietin and IGF-1
• Modifies hormones for excretion or function such as: oestrogen and progesterone, Thyroxin to T3 and Vitamin D3 to calcitriol

Question 20

Explain the location and function of myoepithelial cells in relation to exocrine gland secretion

Question 21

Define the term connective tissue and cite examples.

Answer 21

Connective tissue is tissue that connect, supports, binds or separates other tissues or organs typically having relatively few cells embedded in an amorphous matrix, often with collagen or other fibres. The main cells are fibroblasts, Chondrocytes, Osteocytes, Stem cells.
The main products are Fibres, Ground substance, wax and gel-like materials.
They are made of 3 components:
- Cells - mainly mature fibroblasts
- Fibres (collagen, elastin, reticular fibres)
- Ground Substance (proteoglycans)

Question 22

Describe the function of connective tissue

Answer 22

• Binding and supporting (such as holding skin, gut, lungs, etc. together)
• Protecting (such as bone protecting vital organs, with the fat acting as a shock absorber)
• Insulating (fat underlying skin with the bone marrow holding warm blood)
• Storing reserve fuel and cells (bone marrow and fat tissue)
• Transporting substances within the body (blood and interstitium, which is the space between tissues and organs of the body)
• Separation of tissue (fascia and tendons/cartilage).

Question 23

List the common cell types found in connective tissue (fibroblasts, macrophages and mast cells), and describe their functions.

Answer 23

Fibroblasts - Fibroblasts synthesise and secrete the fibres that lie within the ground substance (extracellular matrix). They are very important in the wound healing process and are the cells responsible of scar tissue.
Myofibroblast - Modified fibroblasts that contain actin and myosin. They are responsible for wound contraction when tissue loss has occurred.
Macrophages - Derived from blood monocytes. They move into loose connective tissue, especially when there is local inflammation. They are phagocytic and can degrade foreign organisms and cell debris. They are APCs and can present foreign material to the T lymphocytes of the immune system.
Mast cells - Look like basophils but are not derived from them. Mast cell cytoplasm contains abundant granules:
- Histamine
- Heparin (an anticoagulant)
- Cytokines that attract eosinophils and neutrophils

Question 24

Describe and discuss the function of the extracellular matrix

Answer 24

The extracellular matrix is a three-dimensional network consisting of extracellular macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite that provide structural and biochemical support to surrounding cells.

Extracellular matrix is the term used to describe a complex extracellular structural network that consists of ground substances and fibres

Question 25

Describe the function of fibres and ground substance in the extracellular matrix

Answer 25

Collagen - Most common protein in our body and makes up between 1/3 and 1/4 of our whole-body protein content. There are 4 types of collagens. Collagen is flexible with a high tensile strength.
Reticular/reticulin - They provide a supporting framework/sponge (they are absent in areolar tissue).
Elastin - Allows tissues to recoil after stretch or distension
Ground substance - A viscous clear substance with a slippery feel due to the high-water content. Composed if proteoglycans and Glycosaminoglycans (GAGs), which are long-chained polysaccharides that attract water to form a hydrated gel.

Question 26

Explain loose connective tissue and their function

Answer 26

Loose connective tissue - Contains multiple cell types e.g., fibroblast, macrophages. Contains two main fibres, (collagenous and elastic). Contains a gel-like ground substance. Their functions include:
- Holds vessels that supply fluids
- Permits cell migration
- Involved in inflammation pathways
- Acts as packaging around organs
- Generally, hold everything in place
- Cushions and stabilises organs

Question 27

Explain dense connective tissue and their function

Answer 27

Dense connective tissue contains few cell types unlike loose connective tissue. They have a high amount of collagen with the arrangement of collagen fibres being parallel. They also have a low amount of Ground substance

Question 28

Classify different types of loose and dense connective tissue.

Answer 28

Loose connective tissue occurs widely in the body as superficial fascia and as an investing fascia around nerves and blood vessels and between skeletal muscles.
Dense connective tissue occurs as dense regular connective tissue e.g., tendons, ligaments, aponeuroses, etc, or dense irregular connective tissue (e.g., dermis, deep fascia, joint capsules, organ capsules etc).

Question 29

Where is the anatomical location of dense irregular connective tissue and their function

Answer 29

• Dermis contains dense irregular connective tissue which contains collagen bundles in a multi-dimensional orientation to enable the tissue to withstand multi-directional tension.
• Deep Fascia covering large muscles or as prolongations between muscle groups to form compartment (anterior and posterior compartments of the arm).

Question 30

What is the anatomical location of dense regular connective tissue and their funciton

Answer 30

Dense regular connective tissues are found in the:
- Tendon - Consists of a cylindrical mass of connective tissue at the end of a muscle. Collagen fibres lay in parallel, densely packed formation in line with the tensile force exerted by the muscle. There is a row of elongated flattened fibroblasts that lie between the collagen bundles
- Ligament - Consists of parallel arrays of collagen fibres
- Aponeurosis - Tendon flattened into a thin broad sheath (e.g., those transmitting the force of the oblique abdominal muscles or the palmar surface of the hand).

Question 31

Describe the anatomical location of loose connective tissue and their function

Answer 31

Superficial fascia (subcutaneous tissue) may be very loose and mobile as it is on the face surface or dorsum of the hand. It is very tight and allows only a little movement of the overlying skin.

Question 32

Where is the anatomical location and function of Mucoid connective tissue

Question 33

Where is the anatomical location of Adipose tissue and what is their function

Answer 33

White adipose tissue - A single enormous lipid droplet with the nucleus, cytoplasm and organelles, all squeezed to one side of the cell. Functions include padding and shock absorber and energy reserve.
Brown adipose tissue - Very few in adults. Multiple small lipid droplets with the nucleus, cytoplasm and organelles all squeezed to the centre of the cell. Provides insulation and energy reserve.

Question 34

Where is the anatomical location of elastic fibre and what is their function

Question 35

What is the anatomical location of collagen fibres and what is their function

Question 36

What is the anatomical location of reticular fibres and what is their function

Question 37

List the signs and symptoms of: scurvy, Marfans syndrome, and osteogenesis imperfecta

Answer 37

• Scurvy - Gum disease and tooth loss, bruising of skin and hair loss, bleeding, poor wound healing
• Marfan’s Syndrome - Abnormally tall, exhibit arachnodactyly, frequent joint dislocation, can be at risk of catastrophic aortic rupture
• Osteogenesis imperfecta - Weakened bones, short stature, presence of blue sclera, hearing loss

Question 38

Explain the causes including the molecular mechanisms behind scurvy, Marfans syndrome and osteogenesis imperfecta

Answer 38

Scurvy - Vitamin C deficiency. Thin collagen fibrils aggregate in some areas to form thicker collagen fibres
Marfan’s syndrome - Mutation of fibrillin 1 gene, which cause elastin tissue to be abnormal and they are surrounded by fibrillin
Osteogenesis imperfecta - Mutation in col1A or col2A gene. Mutated collagen fibres that do not ‘knit together; or not enough collagen is produced or both