Comprehensive Physiology Wiley Online Library

Motor function of anorectum and pelvic floor musculature

Full Article on Wiley Online Library



Abstract

The sections in this article are:

1 Autonomic Innervation
1.1 Lumbar Sympathetic Innervation to Colon, Rectum, and Internal Anal Sphincter
1.2 Sacral Parasympathetic Innervation to Colon, Rectum, and Internal Anal Sphincter
1.3 Sacral Afferent Fibers
2 Somatic Innervation to Skeletal Muscle of Pelvic Floor
2.1 Efferent Innervation
2.2 Afferent Innervation
3 Peptides
3.1 Vasoactive Intestinal‐like Peptide
3.2 Enkephalins
3.3 Substance P‐Like Peptide
3.4 Somatostatin‐like Peptide
4 Motor Activity of Rectum and Internal Anal Sphincter
4.1 General and Historical Considerations
4.2 Intraluminal Pressure Recordings
4.3 Electrical Activity of Rectum and Internal Anal Sphincter
5 Motor Activity of Skeletal Muscle of Pelvic Floor
5.1 Electromyography
5.2 Histochemical Studies
5.3 Force Measurements
6 Influence of Intrinsic Gastrointestinal Nerves on Motor Activity of Internal Anal Sphincter
6.1 Cholinergic Motor Neurons
6.2 Noncholinergic, Nonadrenergic Neurons
6.3 Rectoanal Reflexes
6.4 Vesicoanal Reflexes
7 Influence of Lumbar Sympathetic Nerves on Motor Activity of Colon, Rectum, and Internal Anal Sphincter
7.1 Effect of Electrical Stimulation of Lumbar Sympathetic Nerves
7.2 Effect of Interruption of Lumbar Sympathetic Pathways to Colon, Rectum, and Internal Anal Sphincter
8 Influence of Sacral Autonomic Nerves on Motor Activity of Internal Anal Sphincter
8.1 Effect of Electrical Stimulation of Sacral Parasympathetic Nerves
8.2 Cholinergic Agonists
9 Influence of Sacral Autonomic Nerves on Motor Activity of Colon and Rectum
9.1 Effect of Electrical Stimulation of Sacral Nerves
9.2 Cholinergic Responses
9.3 Noncholinergic, Nonadrenergic Responses
10 Influence of Somatic Nerves on Motor Activity of Skeletal Muscle of Pelvic Floor
10.1 Somatic Reflexes
10.2 Supraspinal Pathways
10.3 Viscerosomatic Reflexes
10.4 Flexor Reflexes
11 Defecation
11.1 General Considerations
11.2 Visceral and Somatic Afferent Fibers
11.3 Sacral Parasympathetic Efferent Fibers
11.4 Relationship Between Eating and Colonic Motility
12 Motor Dysfunction of Colon, Anorectum, and Pelvic Floor Musculature
12.1 Muscle Dysfunction
12.2 Neurogenic Dysfunctions
Figure 1. Figure 1.

Sacral parasympathetic innervation to cat colon. Colonic oranches of pelvic nerve connect with one or two extramural parasympathetic ganglia. Fiber bundles from ganglia connect ganglia with serosal surface of distal colon and midcolon.

From Krier and Hartman
Figure 2. Figure 2.

Relationship between preganglionic neurons in sacral parasympathetic nucleus and pelvic nerve afferents. Neurons in dorsal band (DB) are located primarily in lamina V and VI at base of dorsal horn. Neurons in lateral band (LB) located in lamina VII at lateral border of intermediate gray matter. Preganglionic neurons that innervate colon and rectum are contained within dorsal band. Preganglionic neurons that innervate urinary bladder are contained within lateral band. Visceral afferents are contained in Lissauer's tract (LT) and collateral pathways from Lissauer's tract. LCP, lateral collateral pathway; MCP, medial collateral pathway. Calibration bar, 400 μm. Data based on horseradish peroxidase tracing technique.

From de Groat et al.
Figure 3. Figure 3.

Dark‐field photomicrographs showing relationship between pudendal motor nucleus (Onuf's nucleus) and afferent fibers. A: lumbar (L7) segment; B: sacral spinal cord (S1); and C, D: S2 segment. D shows separation of ON into two parts: dorsolateral and ventromedial. Data obtained from one Rhesus monkey using horseradish peroxidase (HRP) tracing technique; HRP applied to central cut end of one pudendal nerve. ON, neurons in Onuf's nucleus (A, D); LT, afferent fibers in Lissauer's tract (A‐C); LP, lateral afferent projections from Lissauer's tract; MP, medial projections from Lissauer's tract; CC, central canal. Bar: A, 200 μm; B, C, 250 μm; D, 80 μm.

From Roppolo et al.
Figure 4. Figure 4.

Electrical activity recorded from smooth muscle of internal anal sphincter in cats (A‐C) and humans (D‐F). A, B, D‐F: tracings obtained in situ with extracellular electrodes. C: tracing obtained in vitro with sucrose‐gap technique.

A‐C adapted from Bouvier and Gonella . D, E adapted from Wankling et al. . F adapted from Kerremans
Figure 5. Figure 5.

Phasic isotonic contractions of skeletal muscle of external anal sphincter of cat. Each panel shows superimposed consecutive responses at indicated frequencies of pudendal nerve stimulation. Different decay rates reflect effect of spontaneous contractions of smooth muscle of rectuminternal anal sphincter.

From Krier and Adams
Figure 6. Figure 6.

Schematic representation of lumbar sympathetic innervation of internal anal sphincter. Pathway described based on experiments in cats. Adrenergic receptor types based on experiments in cats and humans. NEPI, norepinephrine.

Adapted from Bouvier and Gonella
Figure 7. Figure 7.

Sacral parasympathetic innervation to internal anal sphincter. Preganglionic fibers that originate from neurons in sacral spinal cord synapse with excitatory cholinergic and inhibitory nonadrenergic, noncholinergic neurons located in rectum‐sphincteric region. In cat, cholinergic neurons are considered to provide excitatory innervation mediated by muscarinic receptors. In contrast, circular muscle fibers of sphincter receive only an inhibitory innervation. Transmitter released by noncholinergic, nonadrenergic neurons is not determined.

Adapted from Bouvier and Gonella
Figure 8. Figure 8.

Discharge pattern of motor unit in skeletal muscle of external anal sphincter of cat in response to noxious stimulus [pinch (A, C, D) and light touch (B, E)] applied to mucosal lining of anal canal by serrated forceps and blunt glass rod (tip diam 2 mm), respectively. A, B: abscissa, time in seconds; ordinate, frequency expressed in impulses/s. Horizontal bars (A, B) and bar with arrows (C, E), duration of stimulation. Data obtained in cat with acutely severed spinal cord (L1 and L2 transection level).

From Krier
Figure 9. Figure 9.

Diagram of pudendal motor pathway to external anal sphincter (EAS).

Figure 10. Figure 10.

Electromyographic recordings from human skeletal muscle of pelvic floor. A: puborectalis; B: subcutaneous component of external anal sphincter. Note recruitment of additional motor units during brief voluntary contraction.

Adapted from Kerremans
Figure 11. Figure 11.

Effects of intravesical (A) and distal intracolonic (B) steady‐state pressure on synchronous reflex discharges recorded in pudendal nerve branch to external anal sphincter. Afferent fibers in contralateral pudendal nerve were electrically stimulated. Abscissa, pressure (Torr); ordinate, percent response. A: 5 cats; B: 4 cats.

[○, Data from McMahon et al. ; □, Δ, ▴, •, data from Traxinger and Krier a)
Figure 12. Figure 12.

Discharge pattern of one afferent unit in second sacral dorsal root of cat in response to steady‐state pressure in anal canal. Abscissa, anal canal pressure; ordinate, frequency expressed in impulses/s. Afferent unit was classified as slowly adapting mechanoreceptor considered to be muscle spindle, ○, resting discharge; •, 10 Torr; Δ, 20 Torr; ▴, 30 Torr; □, 40 Torr.

Adapted from Todd


Figure 1.

Sacral parasympathetic innervation to cat colon. Colonic oranches of pelvic nerve connect with one or two extramural parasympathetic ganglia. Fiber bundles from ganglia connect ganglia with serosal surface of distal colon and midcolon.

From Krier and Hartman


Figure 2.

Relationship between preganglionic neurons in sacral parasympathetic nucleus and pelvic nerve afferents. Neurons in dorsal band (DB) are located primarily in lamina V and VI at base of dorsal horn. Neurons in lateral band (LB) located in lamina VII at lateral border of intermediate gray matter. Preganglionic neurons that innervate colon and rectum are contained within dorsal band. Preganglionic neurons that innervate urinary bladder are contained within lateral band. Visceral afferents are contained in Lissauer's tract (LT) and collateral pathways from Lissauer's tract. LCP, lateral collateral pathway; MCP, medial collateral pathway. Calibration bar, 400 μm. Data based on horseradish peroxidase tracing technique.

From de Groat et al.


Figure 3.

Dark‐field photomicrographs showing relationship between pudendal motor nucleus (Onuf's nucleus) and afferent fibers. A: lumbar (L7) segment; B: sacral spinal cord (S1); and C, D: S2 segment. D shows separation of ON into two parts: dorsolateral and ventromedial. Data obtained from one Rhesus monkey using horseradish peroxidase (HRP) tracing technique; HRP applied to central cut end of one pudendal nerve. ON, neurons in Onuf's nucleus (A, D); LT, afferent fibers in Lissauer's tract (A‐C); LP, lateral afferent projections from Lissauer's tract; MP, medial projections from Lissauer's tract; CC, central canal. Bar: A, 200 μm; B, C, 250 μm; D, 80 μm.

From Roppolo et al.


Figure 4.

Electrical activity recorded from smooth muscle of internal anal sphincter in cats (A‐C) and humans (D‐F). A, B, D‐F: tracings obtained in situ with extracellular electrodes. C: tracing obtained in vitro with sucrose‐gap technique.

A‐C adapted from Bouvier and Gonella . D, E adapted from Wankling et al. . F adapted from Kerremans


Figure 5.

Phasic isotonic contractions of skeletal muscle of external anal sphincter of cat. Each panel shows superimposed consecutive responses at indicated frequencies of pudendal nerve stimulation. Different decay rates reflect effect of spontaneous contractions of smooth muscle of rectuminternal anal sphincter.

From Krier and Adams


Figure 6.

Schematic representation of lumbar sympathetic innervation of internal anal sphincter. Pathway described based on experiments in cats. Adrenergic receptor types based on experiments in cats and humans. NEPI, norepinephrine.

Adapted from Bouvier and Gonella


Figure 7.

Sacral parasympathetic innervation to internal anal sphincter. Preganglionic fibers that originate from neurons in sacral spinal cord synapse with excitatory cholinergic and inhibitory nonadrenergic, noncholinergic neurons located in rectum‐sphincteric region. In cat, cholinergic neurons are considered to provide excitatory innervation mediated by muscarinic receptors. In contrast, circular muscle fibers of sphincter receive only an inhibitory innervation. Transmitter released by noncholinergic, nonadrenergic neurons is not determined.

Adapted from Bouvier and Gonella


Figure 8.

Discharge pattern of motor unit in skeletal muscle of external anal sphincter of cat in response to noxious stimulus [pinch (A, C, D) and light touch (B, E)] applied to mucosal lining of anal canal by serrated forceps and blunt glass rod (tip diam 2 mm), respectively. A, B: abscissa, time in seconds; ordinate, frequency expressed in impulses/s. Horizontal bars (A, B) and bar with arrows (C, E), duration of stimulation. Data obtained in cat with acutely severed spinal cord (L1 and L2 transection level).

From Krier


Figure 9.

Diagram of pudendal motor pathway to external anal sphincter (EAS).



Figure 10.

Electromyographic recordings from human skeletal muscle of pelvic floor. A: puborectalis; B: subcutaneous component of external anal sphincter. Note recruitment of additional motor units during brief voluntary contraction.

Adapted from Kerremans


Figure 11.

Effects of intravesical (A) and distal intracolonic (B) steady‐state pressure on synchronous reflex discharges recorded in pudendal nerve branch to external anal sphincter. Afferent fibers in contralateral pudendal nerve were electrically stimulated. Abscissa, pressure (Torr); ordinate, percent response. A: 5 cats; B: 4 cats.

[○, Data from McMahon et al. ; □, Δ, ▴, •, data from Traxinger and Krier a)


Figure 12.

Discharge pattern of one afferent unit in second sacral dorsal root of cat in response to steady‐state pressure in anal canal. Abscissa, anal canal pressure; ordinate, frequency expressed in impulses/s. Afferent unit was classified as slowly adapting mechanoreceptor considered to be muscle spindle, ○, resting discharge; •, 10 Torr; Δ, 20 Torr; ▴, 30 Torr; □, 40 Torr.

Adapted from Todd
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Jacob Krier. Motor function of anorectum and pelvic floor musculature. Compr Physiol 2011, Supplement 16: Handbook of Physiology, The Gastrointestinal System, Motility and Circulation: 1025-1053. First published in print 1989. doi: 10.1002/cphy.cp060127