Lecture 8.1: Internal Surfaces of the Body Flashcards

1
Q

Membrane Types

A

• Mucous membranes (mucosae singular, mucosa)
• Serous membranes (serosae singular, serosa)

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2
Q

Mucous Membranes: Where?

A

Mucous membranes line internal tubes that open to the exterior:
• Alimentary tract
• Respiratory tract
• Urinary tract
• Reproductive tract

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3
Q

The layers of a mucous membrane (3)

A

1) An epithelium lining the lumen of a tube, the type depends on the site
2) An adjacent layer of connective tissue often referred to as the lamina propria
3) In the alimentary tract, a 3rd layer of smooth muscle cells is present: the muscularis mucosae

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4
Q

What are Serous Membranes?

A

Serous membranes are thin, two-part membranes that line certain closed body cavities (spaces that do not open to the exterior)

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5
Q

Development of Serous Membranes

A

During embryonic development, the heart, lungs, and digestive tract develop next to a bag-like cavity, into which they invaginate (turned inside out or folded back on itself to form a cavity or pouch)

This way, they become enveloped by serous membranes

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6
Q

What do Serous Membranes Envelop?

A

• The Peritoneum, which envelops many abdominal organs
• The Pleural Sacs, which envelop the lungs
• The Pericardial sac, which envelops the heart

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7
Q

What do serous membranes secrete?

A

These serous membranes (or serosae) secrete a lubricating fluid that promotes relatively friction-free movement of the structures that they surround

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8
Q

The Pericardial Sac: Outwards to Inwards

A

Parietal Pericardium

Pericardial Cavity

Visceral Pericardium

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9
Q

Pleurae of Lungs: Outwards to Inwards

A

Parietal Pleura

Pleural Cavity

Visceral Pleura

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10
Q

Where do most digestive organs lie?

A

Abdominopelvic Cavity

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11
Q

The Peritoneum

A

Most digestive organs lie within the abdominopelvic cavity, which is covered by the visceral layer of the peritoneum

The cavity wall is lined by the parietal peritoneum

Serous fluid allows movement of the organs during digestion

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12
Q

What is the Mesentery?

A

A double layer of peritoneum extending from the posterior body wall

Supplying blood vessels, lymphatics and nerves to the intestines

It is also a site of fat storage

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13
Q

Retroperitoneal Organs

A

Include (most of) the pancreas and oesophagus, the kidneys, ureters, and ascending and descending colon

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14
Q

The Gastrointestinal Tract

A

Oesophagus
Stomach
Small Intestine (Duodenum, Jejunum, Ileum)
Colon
Rectum

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15
Q

The 4 Layers of the Gut Tube

A

1) A mucosa surrounding the lumen (epithelium, lamina propria, muscularis mucosae), the epithelium is simple columnar throughout, bookended by stratified squamous non-keratinised epithelium

2) A submucosa (loose irregular CT)

3) External layers of circular and longitudinal smooth muscle (muscularis externae)

4) An outer serosa (or adventitia at either end)

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16
Q

Layers of the Mucosa of the Gut Wall: Outwards to Inwards

A

Muscularis mucosae

Lamina propria

Epithelium

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17
Q

Peyer’s Patches (Mucosa of Gut Wall)

A

Aggregations of lymphocytes are often present in the lamina propria, particularly distal ileum where they form Peyer’s patches

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18
Q

The Submucosa of the Gut Wall

A

A layer of loose irregular connective tissue bearing glands, arteries, veins, lymphatics and nerves

Glands within the submucosa

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19
Q

External Muscle of the Gut Wall

A

Two layers of smooth muscle comprise the muscularis externa:

• Outer longitudinal smooth muscle layer
• Inner circular smooth muscle layer

The muscularis externa creates successive peristaltic waves to move luminal contents along the gut under the control of the enteric nervous system

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20
Q

The Serosa of the Gut Wall

A

Simple Squamous Epithelium (Mesothelium)

Connective Tissue

Mesentery (double layer of visceral peritoneum) containing arteries, veins and nerves

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21
Q

Layers of the the Oesophagus: Outwards to Inwards

A

Muscularis externa (comprised of skeletal muscle only in the upper 1/3 of the oesophagus)

Submucosa

Mucosa (Muscularis mucosae, Lamina propria, Epithelium)

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22
Q

Oesophageal Mucosa (3 Layers)

A

Muscularis mucosae: thin layer of smooth muscle

Lamina propria: loose connective tissue bearing blood and lymph vessels, some smooth muscle cells and many cells of immune system

Epithelium: stratified squamous non-keratinized (withstands abrasion)

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23
Q

Outer Layers of the Oesophagus

A

Submucosa: subtending layer of connective tissue containing mucus secreting glands

Muscularis externa: a mix of smooth and skeletal muscle layers (inner– circular; outer– longitudinal) that move food by peristalsis

Adventitia: thin outermost layer of connective tissue to anchor organ

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24
Q

Regions of the Stomach (4)

A

The stomach has four distinct regions:

• Cardia
• Fundus
• Body
• Pylorus

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25
Q

Gastric Glands of the Stomach

A

They are located on the fundus and body regions of the stomach

They produce acidic gastric juice

26
Q

The Main Function of the Pylorus and Cardia

A

Mucus Production

27
Q

Rugae

A

The mucosa and submucosa is folded into rugae when empty

28
Q

Muscularis of the Stomach: Layers and Function

A

Longitudinal Layer
Circular Layer
Oblique Layer

Contractions of the three layers of muscle allows thorough mixing of ingested food with enzymes and mucus to form chyme

29
Q

Gastric Glands in the Mucosa of the Stomach

A

These are simple branched tubular glands lined with simple columnar epithelium

The various types of gastric glands feature different specialised cells that produce mucus, hydrochloric acid, digestive enzymes and digestive hormones

30
Q

Isthmus

A

Stem cells are located in the isthmus (neck) linking gastric pits and glands, and these turn over every 4-7 days

31
Q

Layers of the Small Intestine (Jejunum): Outwards to Inwards (3)

A

Muscularis Externa

Submucosa

Jejunal mucosa (simple columnar epithelium, lamina propria and muscularis mucosae

32
Q

Plicae Circulares

A

Plicae circulares are circular folds of mucosa and submucosa projecting into the gut lumen

33
Q

Peyer’s Patches in the Ileum

A

Peyer’s patches are large aggregations of lymphoid follicles found in the ileum providing immune surveillance

Nodules project into the mucosa, where they are covered with a layer of epithelium with relatively few goblet cells

Specialised ‘M cells’ in the epithelium transcytose antigens from the lumen to a reservoir of immune cells

Immunoglobulins are released back into the lumen

34
Q

The Colon

A

There are no plicae circulares and no villi

Mucosa contains simple columnar epithelium

Goblet cells of the crypts of Lieberkühn are highly productive

The surface epithelial cells absorb water and electrolytes

The colon is supported by adventitia in retroperitoneal regions

35
Q

Muscularis Externa in the Colon

A

The organisation of the muscularisexterna changes

The longitudinal muscle reorganises into three bands known as taeniae coli

36
Q

Respiratory Tract: Conducting Portion

A

Stretches from the nasal cavity to the conducting bronchioles

37
Q

Respiratory Tract: Respiratory Portion

A

Alveolar ducts and alveoli constitute the respiratory portion

This is where gas exchange takes place

38
Q

Olfactory epithelium in the roof of the nasal cavity

A

Absence of goblet cells

Bowman’s glands (branched tubuloalveolar) produce fluid to dissolve odiferous substances

Ciliated olfactory receptor cellsare located in the thick olfactory epithelium

The lamina propria in the nasal cavity is richly vascularised with venous plexuses

39
Q

Trachea and Oesophagus: Fibroelastic Membrane

A

The fibroelastic membrane contains the trachealis muscle, which relaxes when you swallow and contracts when you cough

40
Q

Wall of the Trachea: Outwards to Inwards

A

Submucosa with seromucous (tubuloacinar) glands
Lamina propria
C-shaped cartilage(hyaline)
Epithelium (pseudostratified ciliated columnar)

41
Q

Layers of a Bronchus: Outwards to Inwards

A

Hyaline cartilage (crescent-shaped)
Glands in submucosa
Smooth muscle
Epithelium (pseudostratified ciliated columnar)

42
Q

Structure of Bronchiole: Outwards to Inwards + General

A

Alveoli
Smooth muscle
Epithelium (simple columnar: varies from ciliated through cuboidal)

Note that there is no cartilage to keep the lumen open
Smaller, respiratory bronchioles have no smooth muscle and are lined with cuboidal epithelium

43
Q

Alveoli: Cells Present

A

Type I Pneumocytes
Type II Pneumocytes
Macrophages
Endothelial Cells

44
Q

Alveoli: Type I Pneumocytes

A

Simple Squamous Epithelial Cells

Account for 40% of the alveolar cell population, but cover 95% of the surface area of the alveoli

Facilitate gas exchange with capillaries

45
Q

Alveoli: Type II Pneumocytes

A

Cuboidal

Account for 60% of the alveolar cell population, but cover only 5% of the alveolar surface

They secrete surfactant (compounds that lower the surface tension/ interfacial tension between two liquids, between a gas and a liquid, or between a liquid and a solid)

46
Q

Alveoli: Macrophages

A

Dust Cells line alveolar surface to phagocytose foreign particles

47
Q

What forms the blood-air barrier in alveoli?

A

The membranes of Type I Pneumocytes and endothelial cells (as well as their fused basement membrane) form a blood-air barrier

48
Q

What are alveoli surrounded by?

A

Alveoli are surrounded by a ‘basketwork’ of capillaries and elastic fibres

49
Q

The Urinary Tract: Organs/Structures Involved

A

Kidney
Ureter
Bladder
Urethra

50
Q

Renal Calyces

A

Collecting ducts gather filtrate produced by nephrons

Filtrate is delivered to the calyces (lined with transitional epithelium)

Urine then passes to the ureters

51
Q

Layers of the Ureter: Outwards to Inwards (3)

A

Muscularis Externa
Fibroelastic Lamina Propria
Transitional Epithelium

52
Q

Layers of Bladder Wall: Outwards to Inwards (6)

A

Serous Peritoneum (upper bladder- rest has an adventitia)

Muscularis is comprised of three poorly-delineated layers forming the detrusor muscle (smooth muscle)

Dense Irregular Connective Tissue

Transitional Epithelium

Ruga

Lumen

53
Q

Transitional Epithelium of the Bladder

A

Impermeability to urine conferred by cells with a modified plasma membrane and intercellular tight junctions

Epithelium is distensible

54
Q

The Female Urethra

A

The female urethra is entirely urinary

55
Q

The Urethra: General Structure + Cells Present

A

The proximal region of the urethra (e.g. the prostatic urethra in males) is lined by transitional epithelium

The epithelium of rest of the urethra varies, stratified columnar epithelium is found and regions of pseudostratified epithelium

As with other systems that open to the outside, distal regions are lined with stratified squamous, non-keratinised epithelium

56
Q

Layers of Penile Urethra: Outwards to Inwards

A

Cavernous Space in Corpus Spongiosum
Stratified Columnar Epithelium
Lumen

57
Q

Mucosa

A

The moist, inner lining of some organs and body cavities

Glands in the mucosa make mucus

58
Q

Submucosa

A

The submucosa is a thick layer of loose connective tissue that surrounds the mucosa

This layer also contains blood vessels, lymphatic vessels, and nerves

Glands may be embedded in this layer

59
Q

Serosa

A

A smooth tissue membrane of mesothelium lining the contents and inner walls of body cavities, which secrete serous fluid to allow lubricated sliding movements between opposing surfaces

60
Q

Adventitia

A

The adventitia is the outermost layer of the vessel and contains connective tissue, nerves, and the smaller vessels that supply the vessel wall with oxygen and nutrients (the vasa vasorum)